There are several different kinds of actions that come under the general meaning of ‘attacking’ the Earth – or any other planet, for that matter. The obvious inference is a straightforward invasion, to take over the planet in order to either rule it or exploit its resources.
However, an attack could also be mounted with the intent of either wiping out civilizations or life forms existing there or even destroying the planet itself. The type of attack you intend to make will depend on your ultimate purpose in targeting the Earth. If you’re looking for a suitable environment in which to live and expand your influence, then invasion – or possibly terraforming – is your best bet. If you want to prevent others from exploiting the planet, then you may wish to destroy it entirely. This may also be the case if you consider the existence of the planet itself a danger to you, or if it is in the way of your logistical plans.
There have been suggestions on Earth over the years that offworld civilizations might be sufficiently concerned at the development of such quaint technologies as nuclear weapons, as to decide that these weapons are a threat even over interstellar distances. A threat has to be eliminated, and if your species believes that the Earth is a direct threat, then you will want, rightly, to eliminate that threat. You will want to destroy the Earth and humanity.
Who doesn’t, after all?
There is a temptation, when thinking of destroying a planet or its population, to design a weapon capable of not just eliminating the enemy life form(s), but of completely destroying the physical body of the planet itself. Blowing stuff up is always satisfying.
The most famous example in terrestrial media is the Death Star in Star Wars, an armoured space station the size of a small moon, which is armed with a gigantic projected energy weapon capable of causing an entire planet to physically explode. (The means of this explosion is never quite explained, but may perhaps be the result of heating the interior core beyond the capacity of the rocky crust to contain the gases and pressures thus generated.)
In other propaganda films made on Earth, a similar effect has been achieved by means of explosives introduced to the core via mining shafts, the use of the Illudium PU-36 explosive space modulator, by the sheer overwhelming firepower of massed fleets of capital ships’ weaponries, or by stellar construction equipment. This isn’t as daft as it sounds, when you consider that the gravity well of a planet or star system will affect the travel of particles and waves through it.
In at least one piece of literature, an arrangement of black holes was said to have been used as a barrel to fire projectile suns and planets at target worlds, which is really taking things to unnecessary excess.
Although this temptation for physical deconstruction is quite natural and exciting, your strategic planners and those who determine your military doctrine should be sure to consider all of the information available, before deciding upon the best means to eliminate a planet from the battlefield entirely, should it be necessary or desirable to do so. This is a big decision to make, not just ethically and morally, but in terms of the sheer amount of energy and action required to execute such a massive change to the local order of things.
Assuming you have ascertained the desire and/or certainty to take the Earth out of the equation entirely, rather than to conquer it, you must decide whether to actually destroy its physical form, sterilize the planet so that whatever was problematic there no longer exists, or conduct the extinction of only selected life forms and/or civilizations.
The use of so-called ‘berserker’ devices falls under this type of attack, and some thought has been given to the concept on Earth.
A berserker would be an automated probe which sends out a signal to a planet it visits, to test whether life there has achieved a specific level of sentience and/or technological development. If the berserker device receives a reply (and, naturally, the signal should be offering something that the planetary population would want to reply to), it detonates, destroying the planet. Depending on the design, the berserker may destroy the planet by other means than self-destruction – perhaps returning to the Death Star/giant energy weapon, but the principle is the same.
While it is certainly impressive, and a mark of your power and technological development and ingenuity, to physically reduce a planet to rubble, destroying the Earth completely will undoubtedly be beyond the technology of many spacefaring species.
Planets are, to put it bluntly, built to last, and the Earth is no exception.
To be completely blown apart, in the manner of a victim of the Death Star, or Vulcan in 2009’s Star Trek reboot, the Earth would have to suffer the release of an incredible amount of energy – basically equivalent to the amount of all the potential energy bound up within its atomic structure. For those with a numerical bent, this is something on the order of 2.25 x 10 to the power of 32 joules. That’s billions of times the amount of energy released in any nuclear explosion ever detonated on Earth. Specifically, it would take 50 billion times as much energy – and not a mere 20 nukes as Martha Jones seemed to think in the Dr Who episode ‘Journey’s End’.
In fact, the energy requirement is equivalent to crashing a celestial body with at least 60% of the Earth’s mass into the planet, at a velocity at least equal to the Earth’s own escape velocity, which is roughly 23,500 miles per hour.
That’s such a massive energy requirement that the Moon itself falling out of the sky and crashing into the Earth still wouldn’t be enough of an impact to do anything like the required amount of damage (as the mass of the Moon is only about 1/85th the mass of the Earth). The obvious thought would be that a larger impactor would be more likely to fulfil the requirements, and it’s natural to wonder if something closer to the size and mass of Mars would be good enough to do the job.
It wouldn’t. In fact, not only will Mars falling into the Earth not create the required level of physical destruction – those energy requirements are, really, literally, astronomical – but, believe it or not, this has already happened, and the Earth is still here.
Those of you with time travel capability can confirm or deny this for yourselves, but the Moon is now thought to have been created when an object the size of Mars, and with about 10% of the Earth’s mass, hit the still-forming Earth four and a half billion years ago and smashed it apart. Even this wasn’t enough energy to permanently sunder the planet, which reformed under its own gravitational influence over time.
That said, if you could fire present-day Mars (which has a mass of 11% that of the Earth) into the Earth at a speed about six times greater than escape velocity – 140,000 miles per hour should be right – the velocity should make up for the difference in mass, and successfully destroy both planets.
Venus, however, the next planet sunwards from Earth, has approximately 80% the mass of the Earth, and so absolutely would do the job of pulverizing the Earth to rubble, if crashed into the Earth even at escape velocity. So, what else can we use to blow up the Earth?
Antimatter, and in particular antimatter bombs, are often considered a good option, as matter and antimatter brought into contact with each other will mutually annihilate, releasing almost 100% of the energy stored in the atomic structure of both.
This efficiency of mass-energy conversion is usually focussed upon by people who think of it to the exclusion of how to actually achieve it, however. You may be wondering how much antimatter would be required to release the Earth’s 2.25x10 to the power of 32 of energy. It’s a lot. In fact, you would need 1,246,400,000,000 tonnes of antimatter. Well, actually, you’d need a lot more even than that, because a lot of that energy would be lost in heat and light and so on, rather than in true mass-energy conversion of planetary material. So you can consider the 1.244 trillion tons as the bare minimum, or a starting point.
Letting loose a few anti-atoms, or even a handful of antimatter, is not going to get you your Earth-shattering kaboom.
Since physically destroying the entire structure of the Earth is such a wastefully resource-intensive business, and in fact unlikely to succeed anyway, sterilizing the planet of all life forms is a more practicable alternative in most cases (with the obvious exceptions of the planet being a physical obstruction of some kind, perhaps to the route of a hyperspatial bypass).
There are many reasons why you may intend to completely sterilize the planet, but enabling the stripping of it for resources is perhaps the most likely. Native life forms have a tendency to get in the way of major planetary mining operations, and unless you have a particular need for the use of slave labourers to carry the rocks around, it’s generally more convenient to not have the risk of resistance.
Unfortunately, wiping out absolutely all life on Earth – regardless of how fragile its position is, when placed in the context of the infinite void and darkness of space – is also actually a more difficult proposition than you might think. Terrestrial life has proven itself to be remarkably hardy at times. The Earth has suffered numerous large-scale natural extinction-level events over the span of its existence, and none have ever quite completely eliminated life from the planet.
The most well known (to the dominant native life form) extinction event is the so-called K/T impact at the changeover between the Cretaceous and Tertiary geological eras, 65 million years ago. (No, Cretaceous doesn’t start with a K, despite the acronym.) This event wiped out around 70% of all species, of all types and forms of life, extant at the time. The most destructive extinction event in the planetary history was 251 million years ago, when the Permian–Triassic extinction eliminated a massive 95% of the species on the planet.
The K/T impact is thought by many of Earth’s scientists to have been caused by an 8-mile wide (some say 6 miles, others 9) asteroid 65 million years ago, and left a crater 110 miles wide at what is Chicxulub, in the Yucatan Peninsula. Other scientists believe a structure called the Shiva crater, off the east coast of India, indicates a much larger impact, which could have caused this mass extinction. (The Shiva crater is 370 miles by 250, suggesting an impactor 25 miles wide. It’s possible that both impacts could have resulted from the break-up of a single larger body.)
Not all Earth’s scientists agree that either of these was responsible for the extinction of the dinosaurs. Some believe that other factors, such as volcanic activity, climate change, or simple overpopulation leading to an inadequacy of food supplies were as much responsible. There is also much debate over whether the Shiva crater is in fact an impact crater, or a product of natural geomorphology.
In any case, the use of such large impactors proves not to be as reliable as one might expect, when it comes to genocide. Altogether, 25% of species did survive (including the likes of sharks, crocodilians, Coelacanths, and so on), and none of them had constructed reinforced underground bunkers, which some humans have done over the years as protection in the event of nuclear war.
If the goal is to wipe out all terrestrial species, it would be more effective to alter the chemical makeup of the atmosphere and oceans, rendering them inimical to carbon-based life. This too may leave a certain amount of survivors, however, as there are various smaller single-cell life forms the likes of which are capable of surviving even in such altered circumstances. For example, there are water bears, and organisms that live around the vents of so-called ‘black smokers’ deep under the ocean, at crushing pressures and high temperatures.
No such creatures are sophisticated or likely to offer resistance to invasion, of course, but there is always the theoretical chance that they could evolve to threaten you at some future date. And it’s frustrating to be unable to complete a set.
To put this into perspective, 99.9% of all the species that have ever existed in Earth’s history are now extinct, and yet there are still literally millions of species, from sentient space travellers to single-celled virii, and from avian species that soar in the skies, to strange multi-cellular creatures that can only live in the areas around ocean-bottom vents that leak heat from the Earth’s core. Life on the planet is tenacious in the extreme, and some of it always survives somewhere, no matter what the extinction event.
It would, therefore, be something of a challenge to destroy absolutely all life on the planet, as anything guaranteed to do so – and this would have to be on the order of a massive solar event, such as the Sun swelling into a red giant, and burning the planet to the extent of the sea and atmosphere burning off into space – would be likely to render the structure of the planet unsuitable for the acquisition of resources. If such a planet was ideal for your purposes, you perhaps would have been better off finding a world in such a position to begin with, rather than expending the energy required to have the Earth reach such a state.
Biological warfare would be a much better option, especially if the goal is merely to wipe out humanity and leave the rest of the biosphere intact for use and exploitation. A biological pathogen could be engineered to be inimical to the human species, and other species you want rid of, without harming yourself. Pathogens that would affect humanity are unlikely to affect any invading species, and vice-versa. Humanity has, of course, made it easier to spread a suitably lethal pandemic globally, by instituting a global transport network of pressurized aerial vehicles.
There would undoubtedly be survivors in isolated areas – even with a long-lasting airborne pathogen, the weather patterns of the winds could allow areas of the planet to remain uncontaminated – so you would then have to hunt down and eliminate them, by whatever means.
It is theoretically possible that a virus genetically engineered to be inimical to all carbon-based life forms could eventually accomplish the task, but the likelihood of those pockets of life existing out of contact with each other make it unlikely that true 100% infection could ever be achieved.
The extent of life remaining might well be reduced to something as simple as single-celled organisms, or non-sentient creatures existing in the depths of the oceans, but they would still be there as a symbol of your failure, and may have the potential to evolve into something more threatening later. They would also, of course, be far harder to track down, and detect and eliminate, than groups of large mammals. That being said, it would still be your best way of trying for the complete extinction of life.
If wiping out the dominant species, humanity, will suffice for your purposes, then matters become far more practicable. There are many good reasons for taking out the dominant species on Earth before you invade, but the most important one is to prevent the danger of active resistance. There is a simple way of almost certainly wiping out humanity and so guaranteeing total lack of resistance while you carry out your chosen operations on the planet.
That way has already been touched upon in earlier sections: the use of large natural impactors against the planetary surface. Or, to put it another way, asteroid bombardment. The use of asteroid bombardment will guarantee not just large-scale elimination of population centres, but also changes to the climate of the planet, rendering it uninhabitable by humans. Changing the atmosphere and climate can also be achieved by planetary engineering, or terraforming, as it’s called on Earth, but that is a technique more useful for long-term planning than as warfare, and will be addressed in the chapter on ‘Living On Earth’.
Having mentioned asteroid impacts, it’s time to look at meteor bombardment as a general tactic in assaulting the planet. Bear in mind that even if you don’t intend to destroy the Earth or to wipe out humanity, it is still necessary to eliminate local surface defences prior to invasion, and meteor bombardment is an excellent tactic for this.
The golden rule with this form of warfare is to make sure not to use unnecessary excess energy in delivering these natural warheads to their targets. Such adaptation of natural weaponry has been used in a few dramas over the years.
Where the forces depicted in these dramas have tended to go wrong is in using technology such as mass drivers – using arrays of magnetic linear accelerators to accelerate a metallic mass such as an iron-dense asteroid – to launch chunks of space rock at target planets. For example, in the TV series Babylon 5, the Centauri use mass drivers built into their capital warships to pummel the planet Narn with meteors, turning the whole globe into a ruined dustbowl.
This proved three things: 1) space superiority is effective in besieging a planet from orbit; 2) bombardment with meteors really will do plenty of damage to a planet’s biosphere, and 3) the Centauri are idiots with more money (or resources) than sense.
Why are they idiots? Because they had no need to build ships that use a (probably quite high) percentage of their power to accelerate lumps of rock, so long as the target planet has a gravity well. As all planets do.
The mass driver isn’t that new an idea; they were first thought of as a weapon by Robert A. Heinlein in his 1966 novel The Moon is a Harsh Mistress. In the book, the population of a Lunar mining colony wants to secede from being ruled by the authorities on Earth, and, as part of their campaign, use a linear accelerate built in the vicinity of the Mare Undarum to launch rocks at cities on Earth.
What seems to have been forgotten by later thinkers on the matter of meteoric bombardment is that the Loonies (as the rebels are referred to in the book) need to accelerate their rocky payloads to the Moon’s escape velocity (5,400 miles per hour) in order to get them off the Moon and heading towards Earth. A rock already placed into the gravity well may need a nudge to get it on course to impact with a particular point on the surface, but it won’t need anything like the amount of energy required to impart an escape velocity from a decent-sized body.
From the Centauri point of view in Babylon 5, conducting a general bombardment of the surface as a whole, giving the rock a good shove out the airlock, would have done the job.
Also, because of the simple fact of Newtonian physics – every reaction has an equal but opposite reaction – a spacecraft-mounted mass driver would actually function better as an engine than as a weapon. It is, after all, exactly how rockets work. There’s a gorgeous visual image used in the title sequences of the later Babylon 5 seasons showing one of the main characters standing at a window, in which is reflected the image of rocks being launched from his ship’s mass drivers. Sadly, it does not show the ship suddenly tumbling backwards away from us, which is what should actually have happened next.
In short, do not try using ship-mounted mass drivers to launch your asteroid bombardment. Let gravity do the work; it’s cheaper, easier, and more effective.
This approach is more rarely seen in drama and literature, but is not entirely unknown. Oddly, one of the best examples is in the otherwise comedic film Iron Sky, which is about a group of escaped Nazis who have been hiding out in a Lunar base for decades, who then return to try conquering the Earth. At one point their flying saucers are seen to tow big rocks to release into the Earth’s gravity well while the ships themselves peel away. This is, in fact, the far more sensible and energy-efficient way to do it.
If merely thinning out the surviving populace will suffice for your purposes, you should take note that disease will be rife among most of the animal species after the asteroid bombardment, whether you help it along by introducing suitable pathogens or not.
The large numbers of unburied dead and lack of food and clean water resulting after such a disaster will mean harmful bacteria will spread like wildfire through the surviving population. This is well worth exploiting, so long as you have no need of strong captives, as it will further lessen the likelihood and ability of any resistance to your arrival and your plans. Alternatively, you can always pose as benefactors, curing the pandemic, in the hope of gaining human trust. This may be a worthwhile tactic if you are relatively few in number and require an amount of goodwill and help from the population.
It goes without saying, of course, that if you are coming to Earth by means other than starships, then asteroid bombardment will not be an available option. Also, if you are coming from a parallel Earth or from a different period in the planet’s history, and are human yourself, then using a global pandemic as an option is definitely not a wise course of action, due to the risk of some of your forces carrying the pathogen back to your time/dimension and wiping out that population also. At the very least, you will have to make sure all your own populace is inoculated against the chosen disease.
In that instance, your best option for wiping out the native population may simply be to gain access to the Earth’s national nuclear launch codes, and trigger a global nuclear war. You will have to wait some considerable time afterwards, however, for the radiation levels to settle to a point at which you can safely move in and begin full operations or settlement.
Most hostile extraterrestrial interest in the Earth will be in the form of planned invasion and takeover, though the base motive behind that intention will, of course, vary. Whether it’s a desire for living space, the planet’s chemical resources, strategic position, livestock, or just because it’s fun to conquer a planet and gives your military something to do, there are a number of things you must do correctly.
Before embarking on any military campaign, you must gather information. The successful interplanetary conqueror will always be the one who has gathered every possible piece of knowledge and calculated every possible eventuality. Conquests are made in the research and planning stage, not in the running around screaming ‘it’s game over, man,’ stage. It’s admittedly a truism that no battle plan ever survives first contact with the enemy, but this is why you must be prepared with alternate plans in advance.
Even on Earth, the wisdom holds true that the warrior who knows both the enemy and themselves will always win; the warrior who knows themselves but not the enemy will win and lose equally; and the warrior who knows neither really ought to give up and get a civilian day job.
So, knowing your enemy – in this case human society – is an absolute must. If you are coming from a parallel world, you may already know much of what you need, but not everything; there will always be differences, and even if not, you’ll still be dealing with other nations, whose strategy and tactics are secret to you even in your own identical world. If you’re coming from the past, you will have records and histories, but these are written by the victors, and usually with a political slant, so may be unreliable. It will always be better to infiltrate and investigate yourself – and at least you will have the advantage of being able to pass for a local with authority.
If you’re an extraterrestrial coming by a means – such as a wormhole or matter-transmission beam – that will have you arrive directly on the surface, you will also have to do your research by means of either electronic intelligence gathering (tapping data and communications) or infiltration. If you are unable to infiltrate by stealth, you can always try controlling authorized humans by means of telepathy or even simple bribery. Use of robots and drones is also advised, especially if they can be camouflaged as humans or as other acceptable Earth species that will not arouse suspicion.
Starship crews, however, have the best possible view. Literally. The Earth can be sampled in total from orbit, by all possible kinds of scanners and cameras and sensors. It is a simple matter to map the entire surface, both in the visual spectrum of light for your species, and internally by mass spectrometry, radar, gravitometry, and so on. Using the appropriate sensors from orbit will give you a total picture of the Earth from core to outer atmosphere, as well as showing you where humanity has its military strongpoints, where resource deposits are, and the distribution of life forms. You will also be able to track vehicle movement, and eavesdrop on all electronic communications and broadcasts. Be aware, though, that the Earth has hundreds of languages, and you will need to be able to decode them. (Despite this, you will find from the broadcasts that humans seem to think that all other planets share one single language.)
A warning: Do do your research, but be aware of the limitations of your information. Military secrets, generally, are considered to be the shortest-lived as well as the most valuable, but it’s less often recognized that simple information is also extremely short-lived in a military context.
As with any commander, you must make sure that your information is as precise and up to date as possible. It must be accurate, and it must be correct for the time of your attack. This brings a bit of a paradox, because, on the one hand you will want to be prepared well in advance with all of the information you need, but that information must also be current at the latest possible moment before conquest. There’s no point in knowing where all the defences are before you take off, if they’ve moved by the time you arrive.
As you can imagine, this is especially problematic for those of you crossing the void in normal space, or even at relativistic speed. If it takes you years to reach the Earth, then the information you have gathered absolutely will be out of date by the time you arrive, unless you have some kind of time travel capability that allows you to move back through time as you cross space, in order to arrive at a point at which your information is current and correct.
It would make more sense, therefore, to conduct your reconnaissance and intelligence-gathering from a forward base – perhaps on the Moon or Mars, or at one of the LaGrange points in the Earth-Sun or Earth-Moon system – so that you can prepare to launch your attack from there.
There are several stages to an invasion of a territory, regardless of the scale or purpose of the conflict. Broadly speaking, defences and warning systems must be rendered ineffective – or at least disrupted – before the following sequence can occur: entering the target territory, establishing secure beachheads which can be linked together to form a stable controlled area for the later reception of reinforcements and supplies, eliminating military resistance in surrounding territory, and consolidating control of suppressed territory.
In Earth’s history, invasions have been conducted both by crossing land borders, by landing troops at the coast from maritime ships, and by airborne transport of parachute troops. The most effective landing method for you will depend on your means of transport, and how you arrive at Earth. There is no defensive shielding, so, in order of importance, you will need to deal with the following layers of national defences across most of the planet:
First off, you will need to be sure to neutralize defensive forces on the ground, and eliminate air defences that may intercept your re-entry vehicles. Depending upon how much of the planetary society you want to preserve for whatever reason, your means of dealing with native forces will differ.
If your intent is to preserve and exploit humanity (as slaves, food, or whatever), you will need to be precise in your opening bombardment. Laser strikes from orbit, precision-guided missiles with conventional or antimatter warheads, or low-yield tactical nuclear weapons are all viable options for taking out military bases, command and control centres, and so on.
If you have no interest in preserving the native population, and simply want the planet for its mineral resources or as a strategic garrison, then 20 or so mile-wide asteroids directed to impact on low-lying plains and population centres will eliminate all practical resistance in advance, and save you a lot of time, effort, and logistics in holding the planet later.
It will greatly reduce local forces’ ability to organize and coordinate their resistance if you can shut down as close to all terrestrial communications as possible. Doing so will prevent commanders from issuing orders, field units from making situation reports, governments from executing policy, military units from being directed to where your forces are, and so much more besides.
The silence between the authorities and their populations will also have the effect of leaving the populations confused and frightened. They will therefore be more concerned with panicking over their lack of knowledge than resisting your invasion. Similarly, the authorities, especially in urban areas and near political control centres, will have to divert manpower to police their own populations, thus reducing their numbers available to be deployed to the front lines and bridgehead areas where you will be landing.
Fortunately, advances in technology on Earth have actually made this task simpler, rather than more difficult. A couple of decades ago, bringing down the human communications networks would require eliminating exchange buildings filled with electromechanical technology across the globe. Every country and alliance would have to be targeted separately, as they all have separate technical setups and political systems, as well as different chains of command.
Currently, however, Earth has digital communications enabled by microwave transmissions, along with wireless frequencies, and almost all communications devices use microelectronic technology. All of which is vulnerable to the whims of electromagnetism. A strong enough electromagnetic pulse in or near the Earth’s atmosphere will render all such devices over a wide area completely useless, preventing any signal transmission. In the local parlance, the technology would be ‘bricked’ – in other words as electronically active as a baked lump of clay.
A sufficiently strong EMP might well be able to completely inhibit all such devices across the planet, rendering it radio-dark, and thus preventing any signal communication before your landings. The means to produce such a large EMP are varied, both in natural and artificial means.
The largest and most devastating form of EMP would be a naturally generated gamma-ray burst, either from a stellar event such as a supernova, or from a suitable large solar flare event. Solar weather would have the best chance of blanketing the entire planet with charged protons and electrons capable of taking out vital transformers, satellites, and so on. The US and UK governments, two nations which you will certainly come into contact and conflict with, have both recently produced reports acknowledging that a serious Solar energy event could knock out much of the planet’s power and communications systems for weeks, and possibly up to a year.
The best way to engineer a solar coronal mass ejection, which would send a storm of particles out towards the Earth, would be to generate two massive electromagnetic fields over a sunspot – a darker area in the Sun’s upper atmosphere – and let the protons and electrons build up into a loop of plasma between the fields, which would then rise in temperature well beyond the Sun’s coronal temperature. When the protons and electrons in this plasma reach a terminal velocity of 900,000 mph they join the solar wind. If the particles in the plasma reach the Sun’s escape velocity of 1,390,500 mph or above, they can burst into a solar flare or even a full coronal mass ejection – a blast of plasma shot into space like some kind of weapon.
When this plasma hits the Earth’s magnetosphere, it actually deforms the Earth’s magnetic field, even changing the reactions of compass needles. It also can induce large electrical ground currents in the conductive iron of the Earth itself. This sort of magnetic storm causes aurorae in the atmosphere, damages satellites – or, indeed, visiting and unshielded starships, so be careful about trying this – in orbit, and, if strong enough, will disrupt global communications and wreck electrical and electronic equipment on the surface or in the atmosphere.
However, if your ship is capable of travelling across interstellar distances, and/or travelling faster than light or through hyperspace, it should be capable of generating a suitable orbital EMP pulse. After all, even humanity can do that, which is handy if you’re arriving by wormhole, time travel or dimensional rift, and want to use an EMP to knock out planetary communications. All you will need are some nuclear weapons.
It is well known on Earth that nuclear weapons cause an electromagnetic pulse as a first side effect of the detonation of a fission device. For the widest of coverage of the EMP effect, a detonation at an altitude of 250 miles above sea level is recommended. The area affected by the EMP effect will be a roughly U-shaped area, with 60–70% of the effect being on the equatorial side of the detonation. (That is to say, EMPs triggered in the northern hemisphere will mostly affect areas southward of the detonation area, and those triggered in the southern hemisphere will more affect areas northward of the detonation point.)
The amount of energy radiated will vary according to both the altitude of the detonation and the geographical location. The Earth’s magnetic field is stronger over land masses and closer to the poles. If identical EMP devices were detonated over both the equatorial Pacific Ocean and the cities of the Eastern Seaboard of the United States, the EMP over those American cities would be at least five times stronger.
Use of nuclear warheads to knock out communications over large areas of land is, therefore, not an impractical solution to the planetary communications network. That said, if you’re going to use nuclear warheads you may as well use them strategically to destroy military centres, population centres, and so on while you’re at it, and leave the EMP effect just as a side effect.
Humanity has known about the dangers and effects of EMP for decades, however, and some military infrastructures have their electrical and electronic devices shielded against the effect. Interestingly, as the local geopolitical situation on Earth has drifted away from the threat of an exchange of nuclear warheads, and towards lower-key guerrilla actions, the habit of shielding new equipment against EMP has slipped in many of Earth’s militaries. Not only that, but more modern technology is more fragile, and microcircuits are less robust than the thick copper wiring and cables of the past, so, with these two changes in circumstance combined, much of the Earth’s technology today is actually more vulnerable to EMP than it was at earlier stages of development.
This, of course, is entirely to your advantage.
As the Earth is still not yet a unified society, each of its nation-states has its own militaries with their own command and control centres. These centres are, however, devoted to running operations concerned with other terrestrial nation-states, rather than with planetary defence.
Nevertheless, they will be used to co-ordinate any defence against an assault on the planet as a whole, though it is unlikely that – at least in the early stages of such a campaign – the militaries of rival nations would share their command structures against the common foe.
Many of the main command and control centres belonging to the major military powers are well sheltered, safely ensconced in environs – natural or artificial – proofed against nuclear warheads. In some cases these are specially designed and constructed to be proofed against nuclear strikes, while others are built under natural defences such as mountains, which were already strong enough to withstand such attacks.
Most notably, NORAD and the US Air Force’s Space Command (the clue as to why this base is important is in the latter’s name) are settled beneath Cheyenne Mountain in Colorado. This is where, in the Stargate series of media, the Stargate itself is housed, and the location from which units of Earth soldiers make their forays to other planets. As far as is known, this is still fiction, but you will probably have detected the transmissions on the way to Earth and so be wary of this facility.
Meteor bombardment is, again, going to be the best way to deal with such fortified control centres. Anything over a hundred yards or so across should deal with any underground facility, mountains above them notwithstanding.
Attacks not from space will have to use other means, and this will be tricky for those time travellers and dimension-jumpers relying on the Earth’s own weapons to do the job, since, as stated, these facilities tend to be hardened against nuclear blasts. Infiltration and sabotage will be the best options for such invaders.
Those of you with the use of wormholes or teleportation, on the other hand, can have fun with materializing tactical nuclear warheads inside the nuke-proof fortifications and the inevitable devastating results.
This category of target is probably the most obvious one. Since the Earth only has rockets and missiles as weapons usable against spaceborne enemies, removing them must be a priority for any spaceborne assault.
Although there are large launch sites for manned space missions, in both the Western and Eastern hemispheres, most military missile sites are much smaller, more likely to be hidden, and, indeed, often mobile. This means that asteroid bombardment is less likely to be effective. A suitable EMP burst, as already discussed, will render launch protocols ineffective. While the missile launch systems are down, it is recommended that you use your own missiles with tactical nuclear warheads (if you have them), energy weapons, or atmospheric attack craft to strafe or bomb such sites as they are detected.
Non-spaceborne attackers may not need to specifically target these sites, as the missiles will be less of a threat to materialization or reintegration from a wormhole, or to ground troops. Nevertheless, it’s still a wise move to plan for dealing with them, so that they can’t be used to launch strikes against you on the surface, or to launch satellites that would help the native population with their global campaign against you. To that end, sabotage, or outright commando raids are all on the table as options.
The most important – and dangerous, even to an assault from offworld or from other dimensions or eras – element of Earth’s current defensive capability is the capital warship known as the aircraft carrier.
This, obviously, is a large vessel capable of transporting, launching and recovering warplanes. These leviathans are therefore the vital backbone of the ability of Earth’s larger militaries to project their force and effectiveness to any part of the planet. In essence the aircraft carrier is a mobile military base, which is therefore slightly harder to target and remove than a structure on land. It is vital, however, that you do, as the aircraft carrier can manoeuvre closer to your landing zones or wormhole exits, and deploy warplanes quickly to intercept landing craft during their descent through the atmosphere, or to attack your forces on the surface.
Currently, despite some of the visual footage you may have intercepted that has been broadcast from the planet, all such carriers are in fact surface-based ships, confined to the 70% of the Earth’s surface that is ocean. There are, as yet, no aerial carrier vessels. This has not always been the case, oddly enough. Some 80 years ago, nations such as the United States and Germany did toy with the idea of mounting deployable and recoverable interceptor aircraft aboard dirigible airships. Such a carrier would be able to move anywhere in the Earth’s atmosphere in attempts to evade detection and approach enemy targets.
In reality, however, it turned out that such dirigible motherships were in fact slow, difficult to mount defensive weapons aboard, and prone to exploding and crashing on their own. As better military aircraft, aircraft carriers, and in-flight refuelling techniques were developed, the aerial carrier idea was allowed to fade.
With mobile carrier ships eliminated, you would be best advised to deal with airbases on land surfaces.
Obviously these bases are fixed installations, and so cannot move in order to escape detection and destruction, but any installation capable of launching atmospheric craft that can attack your landing vessels or ground forces is a priority threat that must be dealt with.
Depending on your available resources and intentions for the local life forms and surrounding environs, you can use any method you like for the destruction of such bases, up to and including the use of nuclear warheads, meteor bombardment, or antimatter warheads. It’s worth noting, however, that humanity as yet has no antigravity technology available for their warplanes. This means that, with a few exceptions, their interceptors must accelerate down a paved runway in order to take off. Such runways are easily disabled by blasting craters into them, or blocking them with wreckage, which leaves the interceptors useless, and negates the necessity to waste heavier weapons on trying to break through to more heavily fortified hangars and storage areas.
The exception to this rule is Changchu’an-ni Airbase, in North Korea. This is the world’s only (known) entirely underground airbase, runways included. This suggests that either a) the North Koreans have some form of advanced technology that allows their planes to phase through solid matter, making them the most dangerous interceptors the Earth has to offer, or b) the North Koreans have a really strange attitude to military architecture, but in any case this is one airbase you’ll probably have to drop a meteor on, if you want to make a clean sweep of the airfields.
Other types of military bases – frontline firebases, barracks, training grounds, fuel depots, etc – can be dealt with as you see fit. The important thing, however, is to be certain not to leave any resistance operational within your landing areas or bridgeheads, or behind the front lines of your expansion.
Any bases within your sphere of influence will have to be rendered harmless, by being destroyed or taken over. Otherwise, they risk being centres for organized resistance within your area, and able to attack the flanks of your expansion. This would be highly problematic, and endanger your consolidation of captured ground. Do not allow this.
Clearly, if you are invading from starships, your strategy will be most similar to the 20th century’s use of airborne troops. The advantage to landing your forces from above – as opposed to on coastline or across land borders – is that you are not restricted to those areas on which defences are strongest. Obviously any civilization will put its strongest defences on the borders and the coasts, but from above you can land your troops absolutely anywhere. Obviously you have brought enough troops to hold at least a couple of waves in reserve after you commit your first wave. Never, ever, commit your entire force to a single operation, or even the invasion of a single planet.
The freedom to choose your landing sites at will is doubly advantageous if you have been able to destroy or otherwise negate the target’s military power and infrastructure in advance. If you haven’t managed this, then your strategy must include picking suitable landing zones that will meet the balance of allowing you to establish bridgeheads in vital areas quickly, while maximizing the response time from local forces.
Pro-tip: since you can monitor transmissions around the Earth from orbit, you should be able to determine which types of signals and media are used by humans, which are even known to humans, and by extension, which are unknown. You should therefore make sure to keep any communications between your forces to those signals and frequencies, which will not be detected or interpreted on Earth.
If you are operating to a particular time schedule, make sure to synchronize your timekeeping devices before you reach the Earth, and work to a plan, rather than openly transmitting obvious countdowns or navigational signals to each other. Repeated sequences of signals between vessels prior to an attack should be avoided at all costs, because even if your code is incomprehensible, the fact that it is a slightly changing repeated sequence will give the game away.
Maintain communications silence, at least as far as Earth’s ears are concerned, and your actions will be far more of a successful surprise.
When it comes to actually landing on the physical surface of the planet, it is tempting to choose landing zones that are hidden or camouflaged. Warfare, after all, is so often a matter of deception; appear to want to land in one place, but do so in another, look weak when you’re strong, and so on. This is a mistake when landing from orbit, partly due to the velocities involved in picking a precise location, and partly because – unless your landing vehicles are fitted with cloaking devices, or some other form of stealth technology – the landing craft will be visible and detected by radar on their descent.
The important factors for choosing a landing site, therefore – and especially for a major landing of troops in force – are:
1) That the landing area should be physically safe and stable enough to support the type of vessels you’re landing
2) That the landing field be over a large enough area to take many troopships and support vessels
3) That there be enough room for ships that overshoot to still arrive within a defensive perimeter
4) That the landing zone be defensible from counterattack by terrestrial forces.
Taking these requirements in order, the first priority is that your landing area be safe. This means that you ought to be looking for a wide-open space which has solid enough ground to support the weight of your landing craft. If you’re using craft which can land, debark troops, and then take off again, you will probably want bedrock as close to the surface as possible.
This means you need a flat surface. Not a steep slope, not a place strewn with boulders higher than your undercarriage, and definitely not the middle of a forest. It may look cool to see transport ships descend directly into forest and jungle, but this would in reality lead to their hulls being crumpled and punctured in a most harmful way. Trees may be made of wood, but old trees, full-grown, are surprisingly strong, especially along their long vertical axis. In fact, when an object from space exploded in the skies of Tunguska in 1908, flattening hundreds of square miles of Siberian forest, the trees directly underneath the airburst were the ones still standing (albeit stripped of branches).
You do not want your landing craft to end up impaled on a tree trunk like a cocktail sausage.
This is assuming you wish to land properly at all, of course. If you intend to bring your transports down to almost the surface, and have your troops rappel down, or use some form of personal jetpack to descend, or just jump, then you can land them anywhere, regardless of the terrain in the immediate vicinity. However, you will need to establish transport hubs where individuals and materiel can be embarked – troops finishing their tour, injured troops being evacuated for treatment, prisoners, materiel you’ve captured – you will certainly have to land those vessels in order to embark for ascent.
You may also, for convenience, use disposable capsules designed only for atmospheric entry and impact with the surface. In this case you may prefer to look for regions with relatively deep layers of soil and sand which can absorb the impact, or even look for landing zones in marshy areas or in the oceans.
Be aware, if you are landing at sea, that you will need support craft already on station to recover the incoming troops or materiel, or else will require your incomers to be amphibious. It would also, of course, be possible to deliver submersible amphibious vehicles into the oceans in this way, which would largely avoid the problem of having your landing craft exposed to counterattack from terrestrial military forces after reaching the surface – though they would subsequently be so exposed when reaching land, and coastal regions are more likely to be defended against incursion anyway.
If you are invading through teleportation or wormholes, or from an alternate Earth either in a parallel dimension or a different time zone, by a means involving some form of materialization or physical reintegration at your destination, you will have to be aware of the range of physical variation in the surface of the Earth. Materializing, for example, inside the solid rock of a mountain will put a sudden stop to your invasion plans.
It is acceptable to pick a transference area, which will be concealed from the native forces, though it must still be large enough for your troops and equipment to be mustered for their advance, and also defensible.
It would also advisable to pick a transition region capable of aiding aviation, so that you can bring aircraft through, either on the ground – in which case you’ll want a bridgehead site large enough to have a runway built – or in the air, so that aircraft can be flown through.
Once your forces have established a suitable forward base from which to be resupplied and launch missions, you will need to defend that base.
How best to defend these forward bases? One important factor, once humanity’s ability to launch air strikes and missile strikes against you has been negated, is to ensure there’s clear space around the perimeter in which you can see potential insurgents coming in their attempts to destroy or steal your ships and technology.
Parking in a city centre heliport is a bad idea, no matter how pacified the city, as the rubble and standing walls will provide plenty of cover for approaching enemies (or, indeed, for fleeing prisoners). Plus, of course, the remnants of the buildings will make bad ‘footing’ for your craft to land neatly on. This is one of many mistakes made by the Daleks, in both the TV and movie versions of The Dalek Invasion of Earth.
The Empire in the Star Wars films is just as foolish with their installations. When a shield generator was necessary to project an energy field around their second Death Star (itself a waste of time, effort, and money, of course), from the moon called Endor, they seriously misjudged how it should be done. Building a facility in the dense and huge trees of a forest that is home to a native species capable of organized resistance would be a big mistake.
Dropping a rock a few hundred yards across into the forest would clear it for miles, and allow a far safer installation to be constructed at the centre of the crater thus excavated. This would have had the double advantage of eliminating the problematic natives for miles around, and leaving an open killing ground around the facility, across which any approach could be viewed and dealt with.
It comes back to asteroid bombardment again. When you absolutely, positively need to kill every motherfrakker in the LZ, accept no substitute.
Alternatively, depending on how solidly-built your ships are, take a tip from the human command and control centres and bury them under hills and mountains. This will prove protection against strikes up to and including nuclear weapons.
Those of you not arriving in ships would be advised to follow that protocol also; build bunkers into and under hills, for the same reason. Maintain weapons emplacements and guard posts on the surface above, against encroaching ground forces, and be sure to maintain the high ground. Also be sure to install anti-aircraft systems, either in the form of missiles, automated weapons, or energy weapons. However you arrived, if you have the ability to cloak your ships and facilities, do so. Also always be sure to make use of whatever force shield technology you have.
Once you are firmly settled on the surface of the planet, it will be time to conduct operations, both military and objective-related, on the surface.
REPEAT OFFENDERS
Some species and cultures have attempted to invade the Earth more often than others, if terrestrial fiction is anything to go by.
The most common invaders of the Earth have always been the natives of that belligerent red planet, Mars. Even not counting the different versions of War of the Worlds, there have been so many different types of Martians in other books, comics, movies, and games, that there’s no question of the natives of Mars being the number one attackers of the Earth. Different authors, artists and filmmakers have ascribed totally different natures, capabilities and motives to the Martians, but their homeworld and desire to conquer the Earth and wrest it from the grip of humanity has long been a constant factor that links almost every interpretation of the natives of Mars.
Runners-up in the table of making the most repeated attempts to conquer the Earth is probably a single race who have graced the world’s TV screens many times – the Daleks. Although not every appearance they have made has involved them attacking the Earth directly, they have attempted to conquer and/or destroy the Earth a total of 11 times on screen alone and more often still in audio, comics and novels.
The various cosmic entities of H. P. Lovecraft’s Cthulhu mythos have exerted their baleful influence on Earth from distant times and places quite often, but it’s debatable as to whether they’re truly invaders, as they tend to just influence minds from afar, and usually when humans have made contact with them first.