Caesar owed a debt of gratitude to his uncle Marius for the finely tuned army he commanded. His soldiers were not the privileged elite who could afford to equip themselves and once dominated the Roman army. They came from the farms and slums of Rome. It was Marius who started to bolster his armies by training the poor to fight for money rather than glory and secured their allegiance.

The fate of the army, and Rome, was in the hands of Caesar’s centurions. These officers were responsible for training and disciplining the troops and leading them into battle. Centurions earned their rank by various means. Some were elected, some were appointed by the Senate, and some were promoted from the ranks. Caesar often chose soldiers who displayed uncommon valor to serve as centurions. This was a great honor, but one that carried considerable risk. The centurions, easily identified by the horse-hair plumes atop their helmets, always fought in the front rank and suffered the highest casualty rate in the army.

Centurions’ experience and insight was valued among Roman generals, earning many a role in sessions to plot battle strategy. Much like a modern-day army captain, each centurion led a unit, known as a century, of 100 soldiers. Ten cohorts of six centuries each comprised a 6,000-strong legion, which Caesar now aimed at Rome’s rivals in Gaul.

Mechanics of Warfare

Training consisted of repeated daylong hikes, under the full burden of weaponry and equipment expected on the battlefield; drills and maneuvers; and close inspection by centurions. The legionaries’ individual arsenal included a pair of eight-foot javelins – deadly to at least twenty yards – and, for closer combat, a short-bladed sword. A full-body shield, armor of leather and iron, and a helmet added weight and protection to their ensemble.

Building forts and roadways and repairing weaponry - from close-combat arms such as lances, shields, and swords, to the Roman artillery - fell to a squadron of engineers.

Roman artillery consisted of various devices to launch projectiles, the most important of which was the torsion-powered Ballistae. A Ballistae resembled a large crossbow mounted on a solid frame and could hurl a large rock - perfectly round ones were preferred for accuracy - over great distances. A Ballistae had enough brute force to bring down a wall or rupture a fortified rampart, yet was accurate enough that it could be fired at a single soldier. Ballistae made a loud, whirring sound when fired, followed by the whoosh of the stone as it flew toward its target. Enemy troops were terrified of it.

The Roman legions were augmented by provincial recruits and hired mercenaries. Gaul and Germany were hotbeds for cavalry men. Crete and Egypt typically trained the best archers. And the Balearic Islands sent fighters adept at slinging rocks. Many enlisted with the hopes of becoming Roman citizens.

Conquering Gaul

Caesar’s combined force, once sharpened for battle, first targeted a Helvetii horde in pursuit of spoils in southwestern Gaul. Caesar planned to intercept them on the north bank of the Rhone River. Undaunted by their great numbers – 100,000 hardened warriors to his roughly 6,000 (one legion plus a few local recruits) – Caesar set up a barricade, entrenching the bank and cutting off access at Geneva. There, his troops demolished the only bridge. The Helvetii had no option but to turn back.

Caesar took advantage of this victory to bolster his forces, charging chief of staff Labienus with holding the river while he rushed to Italy and mustered five fresh legions. Hemmed in on all sides by mountains, the Helvetii followed a route north that took them through lands belonging to the Aedui, a Gallic tribe allied with Rome.

For two weeks, the Romans pursued their enemy – still three times their number - but never engaged them directly. Then, facing a food shortage, Caesar led his troops to the Aeduan stronghold of Autun to obtain supplies. The Helvetii, believing the Romans were retreating, prepared to attack.

But Caesar seized the high ground. He positioned his troops on the slope of a steep hill, with a pair of reserve legions ready to descend from the crest. From this vantage point, the general hoped he had evened the odds. Caesar roused his army, urging them to fight bravely.

As the sun reached its zenith, the Helvetii swarmed the base of the hill, hoping to crush the Romans by sheer weight of numbers. But Caesar’s men rained down javelins on the Helvetii front line, then advanced on them with swords, driving them back. By late afternoon, the battle was won. Caesar’s cavalry chased and slaughtered their enemies. Surrendering survivors were spared with orders to retreat home. Caesar had shown that he was a master at military strategy and was regarded by many as a born leader.

Caesar learned more about the sprawling region that was Gaul, and he was astonished by the diversity of cultures he encountered. He was particularly impressed by one region of Gaul where land was communally owned and farmed and where each of the country’s 200,000 men served in the army on a rotating basis. Each year, half of them served in the army, while the other half tended the country’s farms, most of which raised livestock, as it was easier to move animals than defend croplands. The two contingents changed places annually, with the farmers joining the army and the soldiers returning to the farms.

These Gallic people, despite their civilized and well-ordered martial society, allowed their children to grow up wild. Children bathed in icy streams, hunted in the mountains, and ran about wearing little clothing. They also learned to ride as they grew up and were became remarkable horsemen, despite their lack of saddles or bridles. They guided their mounts with their knees and hands. These animals were so disciplined, Caesar noted, that if a man dismounted in the heat of a battle, his horse would remain standing in place until its master leapt on again.

Caesar’s reputation brought him new allies. Gallic chieftains flattered him, pledged their support, or pleaded for his help. He was quick to insert himself into the conflicts between warring nations or tribes. It hardly mattered to him which side he stood with. The end result was almost always the same: Caesar won dominion over both.

In one instance, the Aeduans, a tribe comprised of a mix of several diverse groups, had unwittingly unleashed a new threat on the territories of Gaul. To gain an advantage in a long-time conflict with a neighboring tribe, they had employed German mercenaries, who showed no loyalty in victory. The German chieftain, Ariovistus, recruited thousands more mercenaries to mount a full-scale invasion.

Ariovistus had been a friend to the Romans, and since Caesar bore him no real animosity, he first attempted a negotiation. By way of messenger, Caesar sent word to Ariovistus that they needed to talk and asked him to appoint a time and place within Gaul for that face-to-face meeting. The German balked at this request, saying he would not enter Gaul without an army and insisting that any meeting would have to be on his territory.

Taking this as insolence, Caesar dispatched with the pleasantries and warned the German commander that Gaul was under Roman protection and that an invasion would be met harshly. Further, he demanded, hostages taken among the Aeduans must be returned unharmed.

Word of Caesar’s military prowess had not reached Ariovistus, and so he did not fear his opponent. He brushed off the Roman’s demands and pledged to crush any Roman resistance. “The Aeduans,” Ariovistus said, “tried the fortune of war with me, and were overcome; and they must abide the issue. The Romans manage their conquered provinces as they judge proper, without holding themselves accountable to anyone. I shall do the same with mine. All that I can say is, that so long as the Aeduans submit peaceably to my authority, and pay their tribute, I shall not molest them; as to your threat that you shall not disregard their complaints, you must know that no one has ever made war upon me but to his own destruction, and, if you wish to see how it will turn out in your case, you may make the experiment whenever you please.”

Goaded into battle, Caesar assembled his troops in the Aeduan stronghold of Besancon, where the locals spread frightening stories of the might and savagery of the Germans. Panicked and fearful, the Romans tried to convince Caesar to quit the campaign. Some, sensing imminent defeat, wrote their wills. This lack of faith disgusted Caesar, who reminded his men of their victory against the Helvetti and that the supposedly invincible Germans had been beaten before by his uncle Marius. He shamed them and reminded them of their sworn allegiance to Rome and their duty as soldiers to follow wherever he led. He boasted that he, too, would crush this enemy, even if backed by only a single legion.

The general had convinced his troops that another victory was at hand. The legions were now eager to engage the Germans, but Caesar, despite his insistence on taking the offensive, held out a flickering hope that war could be averted. As the two armies met, some fifteen miles from the Rhine, Caesar determined he was badly outnumbered. Ariovistus hesitated and sent a message to Caesar indicating that he was open to discussions. Caesar agreed, but both sides approached the conference with extreme caution.

The meeting took place on a hill at the center of an open plain that separated the two camps. Each commander was accompanied by a small cavalry to stand guard at each end of the rise, with ten men on horseback to join them at the summit. Caesar and Ariovistus talked at length, never dismounting from their steeds, but both held their position and the standoff continued.

Within days, Ariovistus made another overture, requesting another meeting with Caesar, or barring that, one of his chief officers who could be trusted to convey his message. Caesar, sensing treachery, refused to meet with Ariovistus and sent a common messenger to take delivery of the German’s communication. The messenger and his escort were taken prisoner the moment they set foot in the enemy camp.

Battle seemed imminent. Then nothing happened.

The mystery behind the Germans’ inaction was solved by prisoners taken in a skirmish: A prophecy had convinced Ariovistus he must wait for the new moon or face certain defeat.

Caesar wasted little time in seizing this opportunity, attacking at dawn on the next day. The Germans reacted quickly, and the battle unfurled with such speed and ferocity that the Romans’ javelins never came into play in close combat.

While Caesar’s men sliced through the Germans’ left flank, they were outmatched on the opposite side of the battlefield. A young officer named Publius Crassus, son of Caesar’s Triumvirate partner, changed the battle’s momentum, calling up reserve troops. Fleeing for the river, the Germans were cut down before they could cross it. Their leader retreated as darkness fell.

One band of Germans, caught in flight, held Caesar’s imprisoned messenger. Relieved of his iron chains and his captors slain, the man told of his ordeal, saying he survived only by luck. The Germans, he said, had drawn lots to determine whether to set him aflame immediately or wait for another occasion to do so. Each of the three rounds of this game had gone his way.

The Roman troops made camp for the winter in the Aeduans’ territory, while Caesar returned to the business of governing in Cisalpine Gaul.

But more trouble brewed that winter of 58-57 B.C. North of Gaul, the tribes of the Belgae had taken up arms, aggression that threatened to spur a Gallic rebellion. Caesar struck first, marching his troops north to the Aisne River and catching the Belgae unprepared. Roman archers and soldiers foiled the enemy’s attempt to circle and block supply lines, ambushing and slaughtering the Belgae as they struggled through the water.

Marching down the Aisne, the Romans swiftly and easily quashed the Belgae resistance, one tribe at a time, until just a small group of rebels remained in the far north, led by the Nervii, who swore to fight until the last man.

The Nervii made their last stand on the banks of the Sambre River. They ambushed Romans setting up camp there, catching Caesar off guard. The Roman defenses were scrambled and disorganized as the cavalry and archers were driven back. Caesar worked to rally his men. He took charge of his hardest-hit Twelfth Legion – most of its centurions had fallen – raising a shield and their spirits as they re-entered the battle.

The turn of the battle came as Labienus, Caesar’s chief of staff, led two legions down the hills and across the river to circle the enemy. Outmatched, the Nervii put up a courageous fight, but by nightfall, only 500 of their 60,000 fighters remained standing.

Admiring their courage, Caesar promised the Nervii survivors – mostly the elderly, women, and children – safe passage home and vowed to avenge any further attacks on them.

One last holdout remained among the Belgae tribes in the north: the Atuatuci. Finding them entrenched in their strongest fortress, Caesar readied his men for a siege and prepared an attack. The Atuatuci feigned surrender, but then moved to attack that night to try to catch the Romans off guard. They failed to surprise Caesar, who had put his sentries on high alert. The next day, the fortress fell. There was no admiration won this time among Caesar’s enemies. He sold them into slavery.

Military Mastery

What is perhaps most remarkable about Caesar’s conquest of Gaul was that nothing in his earlier life had suggested that he would succeed as a general. The historian Suetonius contends that Caesar’s genius for warfare consisted of equal parts caution and daring. Caesar had an instinct for ambushes and never risked having his army caught by surprise. He was also diligent about being prepared for battle.

Suetonius also maintained that Caesar was adept when it came to changing strategies. On some occasions, he made elaborate tactical plans. Other times, he pressed the fight on the spur of the moment, trusting instincts that were usually rewarded with victory. He was particularly clever about launching attacks at the end of long marches, or in bad weather, when the enemy least expected it. Once he had an enemy on the run Caesar never let up, cutting off routes of retreat and attacking camps as they were being dismantled.

Caesar also possessed a remarkable physical constitution. He was a formidable swordsman and an expert rider, though he usually traveled with his army on foot – often, despite his vanity and regardless of the weather, with his bald head exposed. When he came to a river, Caesar was more likely to swim across than waste time looking for a place to ford, sometimes with inflated bags under each arm.

Caesar had astonishing endurance and often surprised his troops with his ability to get from one place to the next before they expected him. On more than one occasion, he sent out messengers to announce his arrival at some forward outpost only to get there in person ahead of his emissaries.

To his army, Caesar seemed a figure of almost mythic proportions. Caesar’s horse, an exceptional animal that was said to have hooves cloven in five parts, was a potent part of this legend. It was still a colt when soothsayers had advised Caesar that whoever became its master would one day rule the world. Caesar raised the horse himself, and it would not permit anyone but Caesar to ride it. Caesar later had a statue of the animal erected in front of the Temple of Venus in Rome.

Caesar was exceptionally brave and calm in combat. If his troops appeared ready to retreat, he would wade into their midst, seizing men by the neck and forcing them back into the fray. He judged his men not by their morality or social station, but by how well they fought. Suetonius wrote that Caesar treated every man in his army with “equal severity and equal indulgence,” insisting on strict discipline only in the face of the enemy. The general meted out swift and severe punishment to any man who deserted or plotted mutiny. But he was generally tolerant of the loose behavior that overtook his troops after a victory, even when it involved romancing local women. “My soldiers,” Caesar declared, “fight just as well when they are stinking of perfume.”

One way Caesar maintained readiness within the army was by keeping his men uncertain as to their next move. He never announced a march more than moments before it commenced, or warned them of a battle until it was joined. Sometimes, he would order them to form up and get ready to move when, in fact, they weren’t going anywhere. Bad weather and holidays were his favorite times for such stunts. Another technique was to simply tell the men under his command to “keep a close eye on me,” only to steal off in the middle of the night, expecting the army to follow him without orders to march. And it did.

Caesar’s campaign in Gaul drove home the fact that success never continued indefinitely, that he would surely be defeated at some point, and that all the glory gained by his earlier triumphs could be lost. Calculating what he might gain by one more victory against what he stood to lose, he grew more cautious and took fewer chances.

Politics

His foothold now well established in Gaul, Caesar again turned his attention to the business of governing his province with a vigor perhaps unexpected of a soldier just removed from a battle of such duration and difficulty. He tended to his armies – restocking supplies, seeking out new recruits – and caught up on the developments in Rome, where his military success was widely celebrated. A fifteen-day festival, the longest ever, praised Caesar for the acquisition of a new province.

Other news from Rome was less encouraging. Cato’s mission to claim Cyprus for Rome was ending, and there were sure to be negative consequences for Caesar. Caesar’s Triumvirate was also threatening to splinter. His partners Pompey and Crassus were feuding again.

To attempt to repair the relationship and secure the Triumvirate’s hold on the government, the three agreed that Pompey and Crassus would ascend to consul in 56 B.C., granting Caesar five more years as governor, after which he would take over as consul and appoint his partners governors of key territories. Appeased, Pompey and Crassus resolved their differences, and the trio again entwined their fates.

A message from his colleague’s son, young Publius Crassus, later that spring stirred Caesar from his Illyrian province and back to Gaul. A revolt was rising on Gaul’s Atlantic coast, led by the seafaring Veneti, who had assaulted Roman quartermasters restocking supplies for Caesar’s army.

Caesar moved to head off the rebellion. He attacked the Veneti by land in their home territory in the Cherbourg peninsula, where the enemy’s advantage came into full view. The Romans chased the Veneti, who slipped from their grasp, boarding their boats and sailing from one town to the next.

The arrival of the Roman fleet set the forces on an even stance, although the Veneti’s 200-ship armada, raining down missiles, towered over the Roman galleys. Even the rams on the Roman ships proved useless against the tall oaken sides of the Veneti’s sailing vessels. Their greatest weapon proved to be long hooked poles that Caesar’s men used to tear down the enemy’s rigging. The Roman soldiers quickly boarded and took over the Veneti’s ships. The conflict was over by sunset as the crippled Veneti ships slunk ashore in defeat.

The next year, 55 B.C., a pair of invading German tribes encroached on Gaul’s Belgae territory. Caesar again assembled his legions, the sight of which motivated the Germans to seek parley. As the Germans continued to plunder and assembled their forces for a battle, the chieftains crafted a story for Caesar, claiming they had been run out of their homeland by invaders from the east and seeking his approval to settle in the Belgian land they had taken. Caesar dispatched his cavalry to cut them down - men, women, and children alike.

In Rome, Caesar’s brutality was condemned by his political rivals. Cato even suggested handing Caesar over to the Germans.

But Caesar wasn’t finished. In his rage, he had a bridge built across the Rhine, and crossing into Germany, his army laid waste to the countryside.

British Invasion

Britain next caught Caesar’s attention. Rebel refugees from Gaul had been taken in by the Britons, who supported their revolts against Rome. But Caesar’s true motivation for invasion was probably the glory that would come with securing this relatively unknown and remote region, in which Roman forces had yet to set foot.

Britain was a curiosity to Caesar and appealed to his thirst for adventure. He sought out merchants who had conducted trade with Britain and who might be able to share information about its harbors and terrain. He gathered a group of them in France and peppered them with questions, which they were ill-equipped to answer. Their knowledge of Britain was scant, reserved to the southern shore, where all of their transactions took place. They knew nothing of the people or military resources of the region.

Next, he dispatched a spy of sorts, an officer named Volusenus, to sail a ship across the Channel to the coast of Britain. His instructions were to gather information on the various approaches, harbors, and the general terrain. A crew of oarsmen was prepared to beat a hasty retreat at the first sign of discovery or danger. The expedition lasted five days and yielded the details Caesar needed to plan his attack.

The Roman commander assembled a fleet of nearly 100 ships. More than eighty would convey his two legions across the Channel. Another eighteen were assigned to the cavalry, which would sail from a separate port about eighty miles away.

As carefully conceived as the invasion was, Caesar was sailing into trouble. The Britons knew he was coming and prepared an impressive welcoming party.

Nine hours after Caesar’s fleet embarked, it was met on the shores of Britain by a well-organized battle line. Cliffs bordering the beach were swarming with soldiers, and at the water’s edge, a cavalry and carriages of war prevented any forward motion by the invaders.

Caesar ordered his ships to approach slowly, stopping just out of reach of enemy missiles. He held this position for hours, waiting for the full force of his fleet to join him. Some ships had been delayed, including the eighteen that carried his cavalry. The hours were spent setting strategy with his commanding officers. The decided to attack without the cavalry.

The Romans raised anchor and moved along the shore, pursued on land by the Britons for some eight miles until they found ground level enough to attempt a landing.

Caesar commanded his galleys to storm the beach. A hail of missiles preceded them. Nearing shore, the larger troopships were grounded, and Caesar gave the order for his foot soldiers to leap from their decks and begin the assault. But they hesitated. The Britons held the shore – a position of power – and Roman legions forced to wade through the water would be at their mercy. The courage of one was enough, though, to light their battle fire. The standard-bearer of the Tenth Legion leapt into the shallows, and his comrades followed, pouring from the ships and sloshing into combat.

Blood stained the shore as Britons and Romans clashed along the craggy beach. Confusion reigned over the conflict, but the determined and disciplined Roman force hammered away at the British line, sending it into wild disarray.

The Britons regrouped and adjusted their strategy. Taking cover in nearby forests, they struck with speed, ferocity, and accuracy. They met Caesar’s encroaching legions step for step, ambushing and slaughtering them piece by piece.

Meanwhile, a storm took a toll on Caesar’s fleet anchored in the Channel. The Romans had missed their opportunity on the beach. Victory was out of reach. Caesar and his troops withdrew at summer’s end, discouraged and embittered.

But Caesar was not ready to give up the campaign. His motivation for another invasion was not just about his reputation. Rome’s economy thrived on imperial conquest. British mines held valuable metals. But the Roman elite’s growing appetite for conquest was fueled more by the prospect of spreading the influence and standards of empire to every corner of the known world.

At Caesar’s instruction, an armada of 800 ships was assembled that winter, and by the next spring, 54 B.C., it was prepared to sail. Five Roman legions and 4,000 cavalry were aimed at the British shore with a renewed determination.

Victory seemed close at hand, at least initially. Caesar’s forces took the coast unopposed. A day later they cut through a British contingent in a furious clash near present-day Canterbury. The Britons regrouped, united by a king named Cassivellaunus. They employed a strategy that had worked before: setting traps and plotting ambushes from the forests and bogs and orchestrating lightning-quick raids. The weather again played a factor. Winds whipped waves against the hulls of the anchored Roman troopships.

Caesar, however, had a new strategy. He aligned with a British king he had met the prior year in Gaul. That alliance grew to include other tribal leaders. The British forces who continued to resist the Romans were crushed over the course of a few weeks, and a peace was brokered. Caesar accepted that arrangement in place of conquest. Word of another uprising in Gaul called Caesar and his troops back from Britain. They would never return.