If one had asked Chester Nimitz in the opening days of 1944 where the direct offensive against the Axis powers lay, he would have said through the Central Pacific—from the Marshalls, past the Marianas, and on to Japan itself. MacArthur’s drive northward from New Guinea was a steadying movement on Nimitz’s left flank. If one had asked Douglas MacArthur the same question, he would have said that the direct offensive led north from New Guinea to the absolute must of the Philippines and then on to Japan. Nimitz’s drive through the Central Pacific was a steadying movement on MacArthur’s right flank. George Marshall, of course, would have continued to say that the principal offensive thrust was the cross-Channel invasion of Europe.
But a follow-up question to these answers that presupposed the occupation of enemy territory—be it islands in the Pacific or hedgerows in France—would have been, What is the ultimate strategic weapon that is bringing the enemy to its knees? “If I had to give credit to the instruments and machines that won us the war in the Pacific,” Bill Halsey offered in retrospect, “I would rank them in this order: submarines, first, radar second, planes third, bulldozers fourth.”1
From the day he assumed command of the Pacific Fleet aboard the submarine Grayling, Nimitz looked to the submarine force—almost unscathed by opening hostilities—“to carry the load until our great industrial activity could produce the weapons we so sorely needed to carry the war to the enemy.”2 Submariners readily assumed this burden, but early in the war, their overall effectiveness was hampered by a host of defective torpedoes.
Given his background in engineering and submarines, Nimitz understood the mechanics, as well as the frustrations, better than most. The principal torpedo of World War II, the Mark XIV, was 21 inches in diameter and 20 feet 6 inches long. It weighed 3,200 pounds, about a fifth of which was its explosive warhead. Steam powered by methane gas, it left a telltale wake.
The Mark XIV came equipped with a Mark VI magnetic exploder. In theory, the torpedo would pass under the hull of a target, because the keel was more vulnerable than its more heavily armored sides. A compass needle in the torpedo responded to the magnetic force of the ship and closed an electrical circuit to trigger the warhead. As a backup, the Mark VI also had a relatively simple contact exploder.
When BuOrd finally admitted that Mark XIVs were routinely running about ten feet deeper than set and thus harmlessly passing under their targets, adjustments were made, but some torpedoes still failed to explode or exploded prematurely. Even when skippers fired for direct impact, the contact exploder tended to crumple on impact before it could send an electrical impulse to the trigger mechanism.
All this made for a crapshoot, and in the early years of the war, a proper hit was more the exception than the rule. It was easy for BuOrd to blame rookie skippers for this record, but when experienced captains came home with reports of one dud after another, the deficiencies of the Mark XIV slowly became obvious. “If the Bureau of Ordnance can’t provide us with torpedoes that will hit and explode,” Charles Lockwood, Nimitz’s submarine commander in the Central Pacific, fumed to Admiral King on a visit to Washington, “get Bureau of Ships to design a boat hook with which we can rip the plates off the target’s sides!”3
In July 1943, a frustrated Nimitz finally ordered his submarine commanders to do what some had already been doing on the sly: disconnect the magnetic component of the Mark VI exploder. That solved the problem of premature explosions, but it took more exasperated skippers and tests against undersea cliffs off Oahu to pinpoint the weakness of the contact exploder crumpling before it could make contact. In response, the support housing was strengthened. “At last,” Lockwood later revealed, “almost two years after the beginning of the war—U.S. submarines went to sea with a reliable torpedo.”4
“Our submarines continue to turn in a fine performance of duty,” Nimitz wrote Halsey in the spring of 1943, at the height of the torpedo frustrations. “With a gradual increase in the number of submarines in the Western Pacific, the Japs’ ability to keep their far-flung island Empire supplied will gradually wane, and the time will come when they will have to make tough decisions regarding the abandonment of this, that or the other distant island base, simply because it cannot be kept supplied.”5
Just how increasingly effective submarine operations became is evidenced by their impact on Japanese armed forces in the field and the Japanese war industry at home. Seventeen percent of army supplies shipped from Japan were sunk during 1943; 30 percent during 1944; and 50 percent in 1945. Just as draining on the Japanese navy was a shortage of fleet tankers that deprived their fleet of the mobility and staying power that would become almost routine among the growing American carrier forces. At home, for example, the disruption of Japan’s shipping lanes from Southeast Asia had reduced coal and ore imports by two-thirds by 1944. By March 1945, “imports of coal virtually ceased and iron ore was cut off entirely,” because the Japanese were forced to use whatever shipping capacity remained to haul much-needed foodstuffs.6
Conversely, the Japanese achieved great initial offensive success with submarines, but then inexplicably diverted them to such mundane operations as resupplying distant outposts. In the first full year of the war, before this change, Japanese submarines almost managed to deliver a deathblow to America’s carriers. Saratoga was crippled and temporaily put out of action by a Japanese torpedo off Hawaii early in 1942. The I-168 sank the damaged Yorktown after the Battle of Midway before it could be towed to safety. Wasp was torpedoed off Guadalcanal. Other warship casualties at the hands of Japanese submarines that year included the sinking of the cruiser Juneau, with losses that included the five Sullivan brothers, and the crippling of the battleship North Carolina.
But rather than push offensive submarine warfare, the Japanese subsequently diverted the vast majority of their boats to nuisance raids, supply missions, and evacuations. Submarines were never used aggressively against Allied merchant shipping—such as the constant flow of ships in the West Coast–Australia lifeline—which suggests that the Japanese simply failed to appreciate the havoc their German allies were causing in the North Atlantic. Japan continued to concentrate on warships instead of merchant vessels, and as warships were generally more protected, Japanese casualties were higher, with less return. Two obvious exceptions were the sinking of the escort carrier Liscome Bay during the invasion of the Gilbert Islands and the sinking of the heavy cruiser Indianapolis during the last month of the war.
By the end of the war, Japanese naval and merchant shipping losses totaled 3,032 ships displacing 10.6 million tons. Of this total, U.S. forces alone—not counting British, Dutch, Australian, or other allies—sank 2,728 ships totaling 9.7 million tons. American submarines led the way, sinking 1,314 ships of 5.3 million tons, followed by navy-marine carrier-based aircraft, accounting for 520 ships of 2.1 million tons.7
These submarine numbers represent 1,113 merchant ships, or 55.5 percent of all merchant tonnage sunk, and 201 naval vessels, or 27.5 percent of all naval tonnage sunk. Of the 288 submarines in commission during the war, 52 were lost by the war’s end. By comparison, the six-year Battle of the Atlantic, waged from 1939 to 1945, claimed 3,500 Allied merchant ships sunk, totaling 14.5 million tons.
Submarine warfare had become much more destructive and far more of a strategic weapon than anything Chester Nimitz had imagined when he wrote his pre–World War I treatise that included launching bobbing telephone poles to masquerade as submarine periscopes. But what about airpower?
First and foremost, airpower had become an inseparable component of sea power. After the attack on Pearl Harbor and the sinking of the British battleships Prince of Wales and Repulse off Singapore, no commander—Japanese, American, or British—dared to launch a major operation without local control of the air. The decisive Battles of the Coral Sea, Midway, and the Philippine Sea were almost singularly carrier air actions. And land-based air continued to show its power, as MacArthur’s air force had done against Japanese transports in the Battle of the Bismarck Sea.
As both Nimitz and MacArthur drove closer to Japan, much of the focus in the Central Pacific turned to seizing island bases from which to bomb the Japanese home islands. Halsey worried that such a focus might give him short shrift in the South Pacific, but Nimitz reassured him otherwise. “You may rest assured,” Nimitz told Halsey, “that my Staff and I will continue to look out for your interests, although it may appear to some of you occasionally that your Force has been forgotten. We have a good over-all picture of what is happening in the Pacific, and will see that you are not left without tools when the time comes.”8
Even before massive B-29 bombers began to rain destruction on Japan—first in small numbers from China and then from bases that would be seized in the Marianas during 1944—Nimitz kept a steady eye on all aspects of the Pacific war. He was convinced that his submarines were wreaking havoc on Japan’s economy long before the B-29s took flight. And the Japanese appeared to agree. Relying initially on a steady flow of natural resources from Southeast Asia, Japan at first showed tremendous economic performance. But even at its peak, Japanese production reached only about 10 percent of the potential output of the American economy. Japan spent most of 1942 consolidating its new territorial gains and waiting for an American response instead of desperately increasing its own economic output and attempting to deliver a knockout blow.9
Meanwhile, America’s industrial output was turning out aircraft carriers, planes, and tanks in record numbers. By September 1943, the Japanese general staff began a study of the war’s lessons up to that time. Based on air, fleet, and merchant ship losses to date, Japan’s declining ability to import essential raw materials, and the looming threat of air attacks on the home islands, the study concluded that Japan could not win the war and should seek a compromise peace. This determination was made after the grand total of U.S. bombers to attack mainland Japan numbered as yet only the sixteen B-25s of the Doolittle Raid. The driving power behind such Japanese pessimism was not American airpower, but American submarines.10
Japan fought on, of course, but a postwar American survey of bombing results found that “by August 1945, even without direct air attack on her cities and industries, the over-all level of Japanese war production would have declined below the peak levels by 40 to 50 percent solely as a result of the interdiction of overseas imports.”11 The massive B-29 firestorm raids against the Japanese mainland late in the war destroyed infrastructure, killed hundreds of thousands of people, and generally demoralized the civilian population. The evidence, however, shows that Japan’s capacity to wage war had already been severely reduced by offensive submarine operations. The B-29s pulverized Japan’s industrial plants, but many of those plants had been idled by a lack of raw materials.
In emphasizing the impact of submarines against Japanese shipping, it should not be overlooked that naval airpower also played an important role in this regard. Witness the number of ships and tonnage sunk by navy and marine carrier-based aircraft, particularly after U.S. carriers struck close to Japan in 1945. There was also a little-known campaign by Army Air Force B-29s to drop mines into Japan’s home island sea-lanes and further sink and disrupt interisland commerce. Some even argue that had this mining effort been implemented sooner than it was, late in 1944, it would have complemented submarine efforts even more and eliminated all measure of Japanese shipping.12
What the B-29 raids did do was bring the gloom and inevitable doom of the conflict home to the average Japanese citizen. The destruction was graphic and pervasive. Premier Kantaro Suzuki, Japan’s prime minister in the closing days of the war, told the Allies afterward, “It seemed to me unavoidable that in the long run Japan would be almost destroyed by air attack so that merely on the basis of the B-29’s alone [emphasis in original] I was convinced that Japan should sue for peace.”13
But even as late as the summer of 1945, from the perspective of Hap Arnold’s Army Air Force, “there [was] no way to escape the conclusion that the B-29 assaults had thus far failed to force a Japanese surrender in spite of the almost indescribable destruction.”14 This left the American submariners in the Pacific the unheralded heroes of the war. As King wrote afterward, “They made it more difficult for the enemy to consolidate his forward positions, to reinforce his threatened areas, and to pile up in Japan an adequate reserve of fuel oil, medical supplies, rubber and other loot from the newly conquered territory. Submarine operations thus hastened our ultimate victory and resulted in the saving of American lives…. Through their efforts the Japanese were much nearer the end in the late spring of 1945 than was generally realized.”15
In the end, of course, it was a combined effort. Nothing can be taken away from the raw heroism of flying near thirty thousand feet, sucking oxygen in a leather flight jacket, while hammering away at enemy fighters or dodging exploding flak—whether in B-17 Flying Fortresses and B-24 Liberators over Hamburg and Ploesti, or in B-29s high above Yokohama. It took guts. It also took guts to sweat in the narrow confines of a submarine three hundred feet below the surface, with explosions rattling every instrument and fitting in one’s boat, or to hunker down beyond a burning German Tiger tank and advance up the road to Berlin.
World War II demonstrated that airpower alone, or sea or land power alone, could not win a war in the twentieth century. It took a combination, and this realization nurtured the unity-of-command refinements that developed during World War II, ultimately resulting in the creation of the Department of Defense.