The Navy's War Against Japan: A Strategic Analysis

In order to visualize clearly the major strategic problems confronting the con­testants in the recent naval war in the Pacific, we must study the conflict objec­tively in terms of the elements of strategy. Alfred Thayer Mahan named these elements half a century ago and his definitions remain as basic and pertinent today as they were in his own day and in the wars of past ages.

One element, according to Mahan, is concentration. The problem is to concentrate strength where the enemy is weak and pre­vent the enemy from achieving a similar concentration against one’s own forces. Another element is communications; that is, lines of supply and replenishment and clear lines for retreat. The problem is to maintain one’s own lines of communication and dis­rupt those of the enemy. In naval warfare such maintenance and disruption, usually obtained by destroying the enemy fleet, is known as “control of the sea.” A third element is positions. In naval warfare these are shorelines and islands capable of being utilized as bases.¹

Defensively considered, an island base serves as a barrier to enemy advance or a threat to his flanks by direct gunfire, minelaying, or sending out intercepting planes, submarines, or surface craft. In its offensive function it serves an advancing force by protecting its flanks by air, surface, and sub­surface and acting as an assembly point for supplies, reinforcements, and repair facilities. Chains of islands thus may function as de­fense lines or “fronts” against an attacking force; or they may serve as routes for ad­vance and retreat and as communication lines connecting forces with their rearward logistic bases. Most of the great island chains of the Pacific Ocean were used by the con­tending nations at one time or another in World War II both as barriers and as high­ways.

If we place before us a map of the Pacific Ocean we perceive that the islands dotting that vast sheet of water group naturally into a grid of lines and bands. (See Fig. 1.) The roughly north-south lines serving as barriers between the Americas and Asia are:

(1)  To the west—Kamchatka to the East In­dies, via the Kuriles, Japan, the Ryukyus, For­mosa, and the Philippines. Obviously this would be a main line of defense for the Asiatic coast, a “front” against seaborne invasion.

(2)  The central line branches off from the above at Tokyo and descends southeastward via the Izu, Bonin, and Volcano Islands, the Marianas, Truk, and Rabaul to the eastern tip of New Guinea and the Coral Sea.

(3)  To the east—When we try to define the eastern defense line we find ourselves embarrassed by a profusion of islands which make the drawing of a single line impossible. We therefore enclose an area or band between a pair of dotted lines— the westernmost descending from, say, Kiska in the Aleutians to Midway, through the Marshall Islands and thence southward through the New Hebrides and Caledonia; the easternmost de­scending from western Alaska southward through Pearl Harbor and the Phoenix, Samoa, and Tonga Islands.

If we examine the Pacific Ocean for island chains so located as primarily to assist ad­vance, retreat, and communications, we again find three lines or bands, this time running east-west. These are:

(1)  To the north—The Aleutians, extended by the Kuriles.

(2)  To the south—From the Tongas westward through the Fijis, the New Hebrides, the Solo­mons, and the Bismarcks, and along the New Guinea north coast to the vicinity of the Philip­pines.

(3)  The central line is less clear. We may indi­cate it as a band or area enclosed by a pair of ap­proximately horizontal dotted lines—the northernmost running roughly westward from Pearl Harbor, passing near Midway and Marcus and thence through Iwo Jima and Okinawa to the coast of Asia; the southernmost running westward from, say, Canton in the Phoenix Islands, past the Gilberts, through the Marshalls, the Carolines, and the Palaus to the Philippines and Indo-China.

We thus have before us a grid of lines and bands which, together with the surrounding continental shorelines, must largely control the strategy of any naval war in the Pacific. This is the gigantic chess board upon which the United States and her allies contended with the Japanese Empire from 1941 to 1945.

In general, as has been noted, the north- south lines served for defense; the east-west, for advance, retreat, and communication. But this is not entirely true, for both the Japanese and the Allies in the early part of the war used the southernmost east-west line as a defense line separating the land-mass of Australia from the Japanese-held Central Pacific; and through much of the war the westernmost north-south lines served as lines of movement and communication.

If the island chains of our grid delineate the major positions of any war between the United States and Japan, it is clear that forces must be concentrated with reference to these lines. But where? Both the American and Japanese navies, nurtured on Mahan, had their answer. “The most important strategic lines,” said the great naval theorist, “are those which concern communications. Communications dominate war.” And he gave a common-sense illustration: “Every military line may be conceived as having three parts, the middle and the two ends, or flanks. . . . Sound principle requires that military effort should not be distributed along the whole of an enemy’s position,— unless in the unusual case of overwhelm­ing superiority,—but . . . distinctly superior numbers should be concentrated upon a limited portion of it. . . . Unless very urgent reasons to the contrary exist, strike at one end rather than at the middle, because both ends can come up to help the middle against you quicker than one end can get to help the other; and, as between the two ends, strike at the one upon which the enemy most de­pends for reinforcements and supplies to maintain his strength.” In brief, strike at that flank nearest the enemy’s line of com­munications. This concept was to affect American and Japanese naval thinking throughout the war. To determine the vital lines of communication in the Pacific area we must consider the causes of the war.

American government leaders, in setting up lend-lease and establishing the Atlantic Patrol against Axis submarines, had as their immediate aim the support of the British nation and Empire. For they saw clearly that the United States, possessing only six per cent of the world’s population, would be in grave danger if ever the Old World, with its huge populations and resources, should fall entirely under the sway of any power or coalition whose aims were inimical to the American way of life. It was necessary, they believed, for reasons of American security, to come to the aid of the British people and thereby retain an ally with bases in or near Eurasia.

It was this not unselfish American interest in the preservation of the British Empire which brought the United States and Japan into conflict. For by late 1941 Japan had reached an impasse. Largely for want of supplies, her armies were bogging down in China, and America had embargoed ship­ments to her of oil, scrap iron, and other materials of war. She must find another source of supply or her war machine would grind to a halt. The obvious source was the East Indies and British Malaya, for here in abundance were materials she urgently needed—tin, rubber, and, above all, oil. Ac­cordingly, Japanese forces began moving southward via Indo-China. The United States, while fighting an undeclared war on the Atlantic on behalf of Great Britain, could not logically permit the Japanese to overrun the British Empire in the Far East. Therefore President Roosevelt in a personal message to the Japanese emperor called a halt, whereupon Japan struck at Pearl Harbor and the Philippines and proceeded with her southward expansion.

Japan’s moves were part of her Basic Plan for the Greater East Asia War, which con­sisted of the following three phases:

(1)  An attack on Pearl Harbor to weaken the United States Fleet; seizure of Malaya and the East Indies as a Southern Resources Area; estab­lishment of a ring of bases as a defense perimeter around the Resources Area, Japan, and the com­munication line between.

(2)  Strengthening of the perimeter into a powerful line of defense bases.

(3)  Interception and destruction of any forces which might be brought against the perimeter or the vital areas within.

From Japan’s point of view the time ap­peared well chosen. She had a mutual as­sistance pact with Germany and Italy. Axis armies were at the borders of Egypt and at the gates of Moscow. Japan had 170 major combat surface vessels in the Pacific; the United States, Britain, and the Netherlands together, no more than 150. By striking a paralyzing blow at the U. S. Fleet based on Pearl Harbor, the Japanese hoped to gain sufficient time to carry out the rest of their Basic Plan. The United States, harassed by a two-ocean war, would not be able immedi­ately to reinforce the depleted Pacific Fleet. Even if American shipyards should greatly step up their output, the new vessels would supposedly be fed westward one or two at a time so that Japan could take them in stride, destroying them piecemeal and ever re­taining her naval superiority. Eighteen months or two years of this sort of defensive warfare, the Japanese calculated, would bring the desired results. By that time iso­lationist elements within the United States, pointing to the fruitless war of attrition in the Pacific, would force the American govern­ment to make a compromise peace which would leave Japan the greater part of her conquests.

But the Basic Plan for the Greater East Asia War was not without jokers. The attack on Pearl Harbor, for example, has rightly been called by Samuel Eliot Morison a “strategic imbecility.” By that act Japan made impossible the ultimate objective of her Basic Plan. For the attack on Pearl Harbor brought the United States into in­stant unity, destroyed or silenced isolation­ism, and rendered it improbable that we would ever agree to any sort of compromise peace.

The rest of Phase 1 was an unqualified suc­cess. For Japan quickly pushed into Malaya and the East Indies and took possession of her Southern Resources Area. Sending one force down via the Malay Peninsula and Sumatra and another through the Straits of Makassar and Molucca, she closed the pincers on Java, the keystone of the East Indies, and trapped American and Allied surface forces in the Java Sea. At the same time she established her defense perimeter: Burma, Malaya, Sumatra, Java, Timor, through New Guinea to Rabaul; thence up through the Gilberts, the Marshalls, and Wake to the northern Kuriles.

Because the United States and allied powers believed that the war in Europe would absorb their full offensive strength, their opening strategy in the Pacific was re­stricted to the defensive. It had two phases:

(1)  Fight a delaying action in the East Indies with expendable forces.

(2)  Establish a defense line against further Japanese aggression from Dutch Harbor to Mid­way, to Samoa, to New Caledonia, and thence westward so as to put a barrier between Australia and the Japanese-held Central Pacific.

This line was to be maintained at all costs. Nothing further would be asked of Allied Pacific forces until victory had been won in Europe and the warhead of power built up in that area could be turned against the enemy on the other side of the world.

By March, 1942, Japan had won her Southern Resources Area. Japanese and Al­lied forces now faced each other across nearly paralleling defense lines in the South and in the Central Pacific. Deep inside the defense perimeter, Japan’s vital “oil line” between the East Indies and the home islands lay beyond the reach of Allied surface and air attack. To the east of the perimeter and safely behind the Allied defense line was the almost equally vital Allied supply line run­ning from the United States to Australia and New Zealand—and also to Burma and the Burma Road. Within three months of the outbreak of war the situation in the Pacific had reached apparent equilibrium.

Japan was the first to attempt to break the lines. So easily had the American-British-Dutch-Australian force in the East Indies been crushed, so readily and so far ahead of schedule had the investment of the Southern Resources Area been accomplished that the Japanese grew contemptuous of the white man’s fighting prowess. They would scrap Phase 2 of the Basic Plan for the Greater East Asia War, not waiting to com­plete the fortification of their easily-won de­fense perimeter. They would immediately expand the perimeter at the south, the center, and the north—and at the same time force the United States Fleet, or what was left of it after Pearl Harbor, into a decisive engagement. (See Fig. 3.)

The first push, the Japanese decided, would be in the south. They would attempt to break the southern defense line at the Rabaul-Solomons flank. An attack on this flank would hurt the Allies most, for near this point ran their vital supply line. Ac­cordingly, in May, 1942, the Japanese sent an invasion fleet into the Coral Sea south of the Solomons to seize Port Moresby on the southern coast of New Guinea. Conquest of this point would strengthen Japan’s de­fenses in the area; and a victory at sea might open the way for the Japanese to push on into New Caledonia, Fiji, and Samoa and thereby cut the United States-Australia communication line.

This strategy of the Japanese was sound. In striking at the flank nearest the main Allied communication line they showed their understanding of Mahan. But they failed, principally because through intelligence activities we had learned their plans in ad­vance. When the Japanese concentrated force at the southeast salient of their defense perimeter, so did we; and in the Battle of the Coral Sea a combined American-Australian force turned back the invasion attempt. We took the same major losses as they—one carrier sunk, another damaged—but we had won a strategic victory because we had foiled their plans and upset their timetable.

The Japanese reply to this repulse was to speed up the next attack. Within a month, believing that we would keep our naval forces concentrated in the south, they brought naval concentration against the Aleutians in the north and against Midway at the center. (See Fig. 3.) Again, however, we had advance information of their plan and therefore shifted our concentration at top speed to the points of expected impact. In the north the Japanese achieved a limited success, making landings in the far-western Aleutian islands of Attu and Kiska. But at the center they suffered their first unqualified defeat of the war. In the Battle of Midway two United States carrier forces met almost the full strength of the Japanese fleet and turned it back, sinking four Japanese carriers. This loss of carriers, planes, and first-line pilots was a blow which Japan could ill sustain. It more than offset the advantage she had won in her attack on Pearl Harbor. She was never able to regain her former margin of superior­ity. The Battle of Midway was the turning point of the war.

Now the United States could shift from the simple defensive to an offensive- defensive. The time was ripe to hit back. But where? Amateur strategists, studying the Pacific area on a north polar projection, pointed to the Aleutians-Kuriles route as the royal road to Japan. But sounder judg­ment took into account the almost insuper­able problems of supply via Alaska and the difficult weather conditions of the Aleutians. Moreover, the northern route was strate­gically wrong. A thrust along this line, even if practicable and successful, would have rolled the Japanese back upon their own sources of supply in the southern home islands and would have shortened their supply line up from the Southern Resources Area. In Mahan’s book this would have constituted an attack on the wrong flank.

An American thrust across the center, where there were few island “stepping stones” would be equally impracticable until the U. S. Pacific Fleet had been greatly reinforced by new construction—a matter of eighteen months yet in the future. On the whole, a thrust along the southern line ap­peared most promising. Extended to the Philippines, an advance in this quarter could eventually cut Japan’s vital “oil line.”

But such long-term planning could not entirely govern Allied action at this early stage, especially since between the Solomons and the Philippines stood the Japanese bastion centered about Rabaul, a formidable complex of strong points which any Allied advance in the south would eventually have to conquer or circumvent—or else be blocked. Moreover, the demands of the im­pending invasion of North Africa left the Allied position in the Pacific woefully weak. Any aggressive action in the Pacific theater at this time would have to be in the nature of an offensive-defensive; that is, an offensive with defensive intent, a move to counter an expected enemy advance.

And where might the Japanese be expected next to strike? Not along the northern line certainly, for the Aleutian route from west to east, terminating in Alaska, was even less inviting than an advance along this line in the opposite direction. Not at the center probably, for the Japanese fleet was now weaker by four carriers than when it had failed in the first attempt. The next Japanese thrust, it was estimated, would be in the south, a renewed endeavor to cut the United States-Australia supply line.

This Japanese intent was foreshadowed by the establishment of an enemy seaplane base at Tulagi, across from Guadalcanal. It was doubly foreshadowed when in July, 1942, the Japanese landed labor battalions on Guadalcanal and began to construct an airfield. This action set the date for the Allied invasion. Guadalcanal must be seized before the airfield could be finished. For, once com­pleted, this field would give the Japanese control of the air over the eastern Solo­mons—to repulse any attempted Allied in­vasion or support a further Japanese advance eastward.²

On the morning of August 7, an Allied amphibious force put ashore on Guadalcanal and adjacent islands 19,500 U.S. Marines, who quickly destroyed or scattered the small Japanese garrisons and labor battalions. The Allies now held the land around the un­finished airstrip and the sea around the is­lands. Three United States carriers nearby gave them a tenuous command of the air over the invasion area.

On August 8, because of heavy plane losses the carriers withdrew, and with them went American air control over Guadalcanal. After midnight on the morning of the 9th, seven Japanese cruisers came down “the Slot,” the passage through the major Solo­mon Islands, and in the Battle of Savo Island sank four Allied cruisers. This loss obliged all remaining Allied surface units to with­draw. The Allies had lost their temporary control of the sea about Guadalcanal. The newly-landed Marines were left without air or surface support.

Guadalcanal, the prize, now lay isolated between the major Japanese base at Rabaul, 600 miles to the northwest, and the American base at Espiritu Santo, 600 miles to the southeast. (See Fig. 4.) The six-months cam­paign which followed may perhaps be most aptly described as a race by the opposing navies to supply and reinforce the opposing land forces ashore on the island.

We began the race with the considerable advantage of having more troops and more supplies on Guadalcanal than the Japanese had and of having physical possession of the unfinished air strip. The Japanese had offset­ting advantages, however, in that their communication line from Rabaul lay among islands with numerous coves affording con­cealment for approaching surface craft. More­over, they began the campaign with pro­tecting land plane bases at Gasmata and Buka and a seaplane base in the Shortland Islands. Later they were to build airstrips still closer to Guadalcanal on Kolombangara and New Georgia Islands. The Allied line, on the contrary, lay across the open, sub­marine-infested Coral Sea, with the nearest bomber base at Espiritu Santo. Both sides were obliged to divert strength elsewhere, notably to the concurrent Aleutians and New Guinea campaigns; but the Allies had the additional heavy burden of the assault on North Africa, scheduled for early Novem­ber.

The Japanese, despite their advantages, failed to recapture Guadalcanal because they did not at first realize the magnitude of the task. They greatly underestimated the number of Marines ashore on the island and retained the bulk of their available ground forces in New Guinea for a push over the mountains against their old objective of Port Moresby, which they considered the greater peril to their positions. When they at length diverted sufficient troops to Guadal­canal it was already too late.

United States Marine Engineers early completed the unfinished Guadalcanal air­strip, naming it Henderson Field, and on August 20 the first American planes were flown in and based there. From the begin­ning to the end of the campaign this strip was properly the focus of all land, sea, and air activity in the area. Henderson Field was correctly assessed by both contenders as the key to the Eastern Solomons.

Because the Americans held the air field they could bring in supplies and reinforce­ments under land-based air protection and operate in the waters surrounding Guadal­canal during the day. But when evening came all Allied surface craft were obliged to withdraw; whereupon Japanese vessels, hov­ering up the Slot, would move in and take over Iron-bottom Sound until near dawn. Rarely did the Japanese venture into these narrow waters during daylight, and every surface action around Guadalcanal resulted from contacts made when Allied vessels outstayed the sun.

The Japanese plan for recapturing Guadal­canal violated the sea-control-land-control order of conventional strategy. Each attempt consisted of at least four parts: (1) capture Henderson Field with troops landed on the island at night; (2) fly in planes to operate from the field and so gain control of the air; (3) bring in surface forces under the Hender­son Field air umbrella and so gain control of the sea; (4) bring in more troops and, with the aid of air and surface bombardment, secure the island.

The Japanese failed in four attempts at reoccupation because they never succeeded in capturing Henderson Field. In August (Battle of the Tenaru River, Battle of the Eastern Solomons), they landed insufficient troops to endanger American positions, and the carrier fleet which was to approach and fly in planes to the airstrip (had it been captured) timidly retired after an exchange of blows with American carrier forces. In September (Battle of Bloody Ridge), the Japanese, this time initially employing only ground and land-based-air forces, failed again because there were still not enough of their troops on the island to wrest the air­strip from the Americans. In October (Battle for Henderson Field, Battle of Santa Cruz Islands), the Japanese repeated the tactics of the August attempt. By this time they had outsped the Allies in the race for rein­forcement. There were by now about as many Japanese on Guadalcanal as there were Americans. But it proved not enough. The Americans retained the field and the large Nipponese battleship-carrier fleet, maneuvering to the north awaiting word of victory on the island, was at last obliged to retire because of fuel shortage. It was while the enemy fleet was on this retiring course that it came under attack by planes from a small American carrier force coming up from the southeast. The Americans lost a carrier in the ensuing battle; the Japanese, a hundred planes. In November (Battle of Guadalcanal) the Japanese made their last attempt to recapture the island. This time they tried to bring in eleven transports full of troops in order to gain an overwhelming preponder­ance of power. But in a series of surface and air-sea actions they lost seven of the trans­ports and two battleships and were thus obliged to abandon the attempt.

The Japanese now withdrew all capital ships from the area and did not employ them again in the South Pacific. During the following year the United States Navy likewise kept its major fighting vessels out of the Solomons area. American carriers and battleships and heavy new construction would be retained at Pearl Harbor until there could be assembled a fleet adequate for the great offensives to come.

By early 1943 Guadalcanal was secure in American hands. There followed the long- drawn-out campaign of the Upper Solomons, in which the Japanese plane losses became increasingly heavy and disproportionate, while Allied naval forces moved steadily westward along the southern communication line. At the same time United States Army forces pushed northward across the eastern tip of New Guinea. Thus Army and Navy advanced on converging courses and in No­vember came simultaneously against the barrier of Rabaul and the Bismarck Archi­pelago. Rabaul they soon neutralized in a series of stunning air blows and boxed it in by invading surrounding islands. The Army, assisted by the U. S. Seventh Fleet, then continued to advance westward along the north New Guinea coast towards the Philippines.

The war had reached another turning point. During the Solomons Campaign the Japanese-Naval Air Force had lost 3,000 land- and carrier-based planes and 70 per cent of its experienced pilots. From this loss the Imperial Navy was never to recover. The Combined Fleet was obliged to abandon the Central Pacific and withdraw behind a new Defense Line, the island chain running from Tokyo southeastward through the Marianas and Truk. (See Fig. 5.) The Japanese Army, meanwhile, had been taking heavy plane losses in New Guinea, where the U.S. Fifth Air Force was to whittle enemy aircraft strength down to near zero within a few weeks of the Bismarcks breakthrough. Clearly this absence of Japanese army and navy air power must be exploited. The Allied offensive-defensive was over.       

The offensive-defensive was over for another reason. The United States had built a two-ocean navy. The war in the Pacific need no longer await the outcome of the war in Europe before shifting to the all-out offensive. At Pearl Harbor Admiral Nimitz had assembled a new U.S. Fifth Fleet around the most concentrated warhead of power in history—the fast carrier task force. The question was, where to use it.

To clarify the reasons for the choice made and the controversies which have followed, it is necessary to consider the vari­ous strategic concepts held by the United States Army, Navy and Air Force. Army leaders, in general, believed that Japan would have to be conquered by invasion and occupation of the Japanese Islands. Hence they considered it necessary to recapture Luzon as a rearward and Okinawa as an advanced staging base. Navy leaders, in general, believed that Japan could be con­quered by defeating the enemy fleet, gaining control of the sea, and starving the Japanese people and war machine into submission through blockade; that is, cutting all im­portant lines of communication to the home islands. The vital line to be severed was of course the “oil line” between Japan and her Southern Resources Area. This line could be cut by seizure of Luzon or Formosa, or it might be intercepted by the less diffi­cult capture of the Marianas. Air Force leaders, in general, believed that Japan was to be defeated by strategic bombing; that is, by destruction of Japanese industrial cen­ters in the home islands by air attack. This would require seizure of the Marianas, and possibly also of Okinawa, in order to secure bases from which B-29s could strike at Japan and return.

No one of these concepts prevailed. The strategy of the American offensive of 1944-45 was aimed at all three. “In any military scheme that comes before you,” said Mahan, “let your first question to yourself be, Is this consistent with the requirements of concentration? Never attempt to straddle, to do two things at the same time, unless your force is evidently so supreme that you have clearly more than enough for each.” Luckily the United States by 1944 had a force so supreme that we had clearly more than enough for all three. We could afford to experiment.

But where to apply this new strength? A glance at the Pacific Ocean Grid (Fig. 1) indicates the possibilities. The U. S. Fifth Fleet could add its strength to that of the U.S. Sixth Army, Seventh Fleet, and Fifth Air Force, now proceeding so encouragingly along the southern east-west line towards the Philippines. This would have favored the Army’s objectives. Or both Army and Navy could have shifted direction and headed straight towards Tokyo, taking off from the Admiralties and proceeding north­westwards via the Truk-Marianas line. This might conceivably have brought Japanese industry most quickly under strategic bomb­ing.

The Chiefs of Staff rejected both plans of simple concentration in favor of a plan of dual advance along parallel and mutually supporting lines.³ The southwest Pacific Forces continued their thrust along the southern axis, while the Fifth Fleet opened up a new axis by striking westward from Pearl Harbor across the Central Pacific. This divided American strength, to be sure, but it permitted the fast carrier task force to operate under ideal conditions. For the chief characteristic of the new carrier force, besides its striking power, was its reach, its mobility, its sea-keeping quality. Supplied, fueled, repaired, and otherwise serviced by mobile units, it could remain at sea almost indefinitely, striking the enemy whenever and wherever he was weakest and- most unprepared. No fighting machine ever com­bined power so well with the ability to sur­prise. Obviously the carrier force would be at its best in the wide spaces of the Central Pacific. And in late 1943 even Navy leaders still suspected that it would prove highly vulnerable operating near a coast line or among such thickly-dotted strong points as the Carolines.

To clear the flank of advance and secure forward bases the Fifth Fleet opened its campaign by staging invasions of the Gilbert and Marshall Islands. The former, especially the bloody assault on Tarawa, revealed the dangers of inadequate preparatory bombing and bombardment. The latter revealed that the Navy had quickly learned the meaning of adequate preparation, for the Kwajalein assault became the model of a “perfect invasion.” After successful running attacks on other Japanese strong points, including the redoubtable Truk (which proved not so strong as suspected), the Fifth Fleet was ready to crack the Japanese Inner Defense Line.

The Fifth Fleet assault on the Marianas in mid-1944 at long last brought the reclu­sive Japanese Fleet out of the Java Sea area, where it had been desperately training pilots to replace the losses of the Solomons campaign. The hasty training proved inade­quate, for in the Battle of the Philippine Sea, American pilots of the fast carrier task force shot them down by the hundreds— the “Marianas Turkey Shoot,” they called it. Once more the Imperial Fleet was stripped of planes. Decimated by American submarine and carrier air attacks, it slipped away west­ward out of reach.

Capture of the Marianas provided the U. S. Air Force with the bases it needed to begin the bombing of industrial centers in the Tokyo area. From these islands also the Navy could step up the submarine campaign which had already gone far towards choking off supplies to Japan and cutting down the Imperial Fleet. For by this time American submarines, lurking on the “oil line” and the Tokyo-Marianas line, had sunk more than 2,000,000 tons of enemy shipping and destroyed a disproportionate share of com­bat craft. It is fairly certain that United States surface fleets, submarines, and air­craft operating out of the Marianas could have gained control of the Philippine and East China Seas. By interdicting enemy shipping in these waters and mining all approaches to Japanese harbors they un­questionably could in time have starved Japan into submission.

But it was considered necessary to recap­ture the Philippines, not only to provide the Army its rearward staging base for invasion of the Empire but also for political and moral reasons. We had, after all, guaranteed the Filipinos independence by 1946. Thus the Southwest Pacific Axis and the Central Pacific Axis converged on the Philippines in the fall of 1944. (See Fig. 6.) So quickly then did the fast carrier task force, utilizing its mobility to the fullest, paralyze Japanese air strength in the area that the invasion was advanced a month ahead of schedule and could be directed at Leyte in the central Philippines rather than in the south at Mindanao, as originally planned.

This time the Japanese used their now-planeless and therefore useless carriers dur­ing the invasion merely to lure the bulk of the U. S. Third Fleet (alternate title for the Fifth Fleet) northward, while Imperial Navy sur­face forces moved in to smash the Leyte beachhead. But the old battleships and jeep carriers of the U. S. Seventh Fleet proved adequate to repulse the enemy. In a series of actions scattered over five hundred square miles, American sea and air forces destroyed all but a fragment of the Japa­nese Fleet.

Following the Battle for Leyte Gulf, the Third Fleet left Philippine waters and headed north to cooperate with Marianas-based B-29s in an air raid on Tokyo. It was as­sumed that the Fifth Air Force could now safely take over the task of covering the Leyte operations. For this task, however, the army planes proved inadequate, princi­pally because their fixed air strips could not be concealed from repeated bombing. Nor could planes from land bases readily achieve surprise over the enemy. Accordingly, the Tokyo raid was canceled and the Third Fleet, now stripped down to the fast carrier task force, was recalled to the Philippines. Here it remained to support not only the Leyte campaign but the entire advance to Manila.

During November, December, and Janu­ary the carrier force revealed new potentiali­ties. Originally the carrier had been con­ceived as an escort vessel. Its function was to cover with a protective air umbrella the surface forces, which were expected to attend to the business of fighting battles. World War II changed all that. Surface forces and carriers exchanged functions overnight. In the new task force the surface vessels be­came the escorts. Battleships and cruisers were equipped to put up an umbrella of anti­aircraft fire, while the carriers sent their planes against enemy forces beyond the hori­zon. Even in World War II the carrier force was for a time expected mainly to carry out the traditional function of all naval forces, to gain control of the sea. Early, however, this new force proved its efficiency in the specialized function of paving the way for and then supporting amphibious operations. In the operations in Philippine waters, the fast carrier task force demonstrated its usefulness in carrying out still another function, that of lending strategic support to troops. This it did by keeping on the move around the northern Philippines, making strikes on Japanese air strips and shipping, not only in the Manila area but as far away as Okinawa, Formosa, Indo-China, and the China coast.

The enemy thus was subject to continual surprise and found no way to concentrate against the fast-stepping carriers. In order to protect themselves against this shifting source of attack, the Japanese tried to be strong everywhere and ended by being strong nowhere. The Americans were achiev­ing the tactical triumph of breaking up the enemy concentration while preserving their own. At the same time they were cutting his communication lines everywhere and render­ing his positions untenable. It was a battle of a mobile air field against immobile air fields in which mobility won hands down. Following this campaign the Japanese air war was reduced strictly to suicide tactics.

With the recapture of Luzon the oil from the East Indies, so vital to Japan’s war machine, was of course cut off completely. The Japanese could not long continue fight­ing. Only once more would the small rem­nant of their once-powerful fleet come out, a foolish suicide mission that accomplished nothing. (“Tradition,” explained Admiral Toyoda.) The U.S. Navy had accomplished its major objective. But the Army and the Air Force had not achieved theirs. The Army still wanted Okinawa as an advanced staging base for invasion. The Air Force needed Iwo Jima as an airdrome whence short-range fighters could accompany Marianas-based bombers in raids over the Tokyo area, and it needed Okinawa in order to get at industrial centers in southern Japan. The last American campaign of the Pacific war was directed against these two points.

The stay of the U.S. Fifth Fleet (back to its old title) off Okinawa brought out a final and widely-unsuspected characteristic of the fast carrier task force—its relative invulner­ability to long-continued air attack. For eight weeks the force was subjected to re­peated raids by waves of suicide planes, prepared to crash their targets, able at the last moment to shift targets under fire. To these attacks were added the constant threat of winged, jet-propelled, human- guided bombs. No fleet in history had ever been subjected to such a vicious or so long- sustained an attack. The valid assumption is that no other type of fleet could have remained afloat under similar conditions.

During the last months of the war the blockade of Japan became complete. Eighty-eight per cent of her total shipping by now was sunk (55 per cent by U. S. submarines, 18 per cent by U. S. Navy aircraft), and the remainder were rendered useless by an aerial mining program which sealed off the Inland Sea and closed every major home-island port. This absolute blockade threw Japan’s economy off balance and created severe and increasing shortages in food, in materials for war production, and in fuel for operations.

What defeated Japan? Not invasion and occupation, for these proved unnecessary. Indeed, post-war investigation revealed that even the threat of invasion had little influ­ence upon Japan’s decision. It was not the atomic bombs or Russia’s entry, for these came after the Emperor and his Supreme War Council had determined to surrender. The United States Strategic Bombing Sur­vey found many factors involved in the Japanese capitulation, chief among which were the feeling of isolation after the defeat of Germany, the blockade, and the bombing of Japanese cities.

It is perhaps impossible now to disentangle the various causes of the Japanese defeat and determine which, if any, was predomi­nant. Certainly, however, the inevitable preliminary was the blow at Japan’s south­ern flank which severed her communications to the Indies. The parallel moves across the south and across the center which culminated at Luzon revealed a true appreciation on the part of Allied leaders of what constituted the enemy’s jugular vein.