Created as a response to perceived shortcomings in their landing craft during operations in China, the new designs were intended to land larger numbers of troops than the earlier designs. The first design, intended to succeed the Shinshu Maru, took that ship’s well deck and added a full-length flight deck for aircraft to take off (but not land) from. The resultant 11,000 ton ship (the Akitsu Maru) resembled an aircraft carrier, but without a hangar, and a well deck for launching 29 landing craft and 4 support vessels, like its predecessor.

Imperial Japanese Army SS craft No.19

Japanese Landing Capabilities

Early in the interwar period, the Washington Treaty had given each of the three major maritime powers a rationale of sorts to maintain an amphibious capability in the Pacific. As the treaty had prohibited the construction of new bases in the western Pacific or the strengthening of existing bases there, a successful strategy in any conflict between the three powers would require the occupation of enemy bases or the recapture of bases lost to the enemy. But by the 1930s, to Britain, the danger seemed to come from the air and ground forces of an enemy much closer to home. In such a strategic context, it was difficult enough to get funds for the navy, let alone the expansion of the Royal Marines as an amphibious force. During these years, professional conservatism, budgetary restraints, and the discouraging conclusions about the Dardanelles campaign also limited the development of amphibious war capability in the British armed forces to the realm of staff studies and the testing of landing craft, vehicles, and equipment in exercises that were theoretically unopposed. Finally, in this period, Britain had no enemy against which amphibious operations would be required. Under such conditions, Britain understandably failed to develop either the doctrine or the forces for amphibious operations.

Of the three major naval powers, the United States had the strongest motivation to develop an amphibious warfare capability, since the Japanese occupation of Micronesia at the outset of World War I had placed Japan directly athwart the path of any American fleet crossing the central Pacific to rescue or retake the Philippines. Japan had been forbidden by the treaty to fortify the islands of the Pacific. But this prohibition in no way lessened the American conviction that the islands would have to be taken by force, strengthened by strong but mistaken suspicions that Japan, prior to the late 1930s, had fortified the islands in violation of its treaty pledge. Thus, with a specific enemy and a specific theater of operations in mind, the U.S. armed forces, through landing practice and staff study, gradually built up an amphibious warfare capability. In this effort, both the major services participated to some extent: the army and navy periodically joined in fleet landing exercises of some scale in both the Pacific and Caribbean in the 1930s and made limited contributions to the drafting of the tactical manuals that served as doctrinal guides for amphibious operations.

But because the tactical priorities of the two services lay elsewhere, the U.S. Marine Corps was left to develop American amphibious warfare doctrine and thus carve for itself a mission and a professional raison d’être, which the corps has never relinquished. The development of that doctrine and the weapons, equipment, and force structure to support it have been discussed in other publications and are beyond the scope of this book. Suffice it to say that the Marine Corps’ recognition of the terrain and configuration of the Micronesia beaches, which it had targeted for its operations, forced upon the Marine Corps tacticians the doctrinal realities that their British and Japanese counterparts were not obliged to confront in the interwar period. The narrowness of the low islands of Micronesia ensured that landing operations would be met with fierce enemy opposition at the water’s edge and would therefore require the most careful planning, the most effective transport loading, and the most precise coordination with naval gunfire to be successful. The traversing of the coral reefs surrounding most such islands would necessitate the employment of transports and amphibious vehicles not yet in the arsenals of any maritime power. The flat terrain of the Micronesian atolls meant that even high-velocity and flat-trajectory gunfire might not destroy the low bunkers dug into the atolls’ coral and sand. In time, the elements of the Marine Corps’ amphibious warfare capability—unified command, combat loading, adjustments in naval gunnery, closely controlled ship-to-shore movement, amphibious landing craft, and specialized air support—came together and found expression in the kind of war that neither the British nor the Japanese armed forces had seriously considered.

The development of an amphibious landing capability offers something of an exception to the otherwise dismal record of noncooperation between Japan’s two armed services. Since nearly all of Japan’s modern wars were fought outside the home islands, of necessity, the army’s initial operations—landings on an enemy coast—required the navy’s support, a fact remarked upon with some irony by Adm. Yamamoto. Japan was thus one of the first nations to understand the importance of modern amphibious operations, without which it could not hope to establish a military presence on the Asian continent. The navy’s cooperation in debarkation of army troops on Korean shores during the Sino-Japanese and Russo-Japanese Wars had set the tone for the amphibious operations of the future: unopposed landings, often at several landing sites simultaneously, undertaken at night to achieve surprise and to have control of the coastline by dawn.

Until the 1930s, however, neither service maintained a force that had landing operations for its primary mission, as did the U.S. Marine Corps. The army’s role in these wars was principally devoted to the great land battles inland, and therefore, its initial interest in amphibious operations was slight; it was the navy that maintained a modest capability to project its power ashore. Most Japanese warships had a portion of their crews (usually less than a third) designated for use as a rikusentai (naval landing party) composed of sailors who had been given a modicum of infantry and small-arms training and who could be put ashore should the need arise. In riverine China, particularly at Shanghai and on the Yangtze, these shore parties were most often used. There, Japanese gunboats shared the rivers with similar vessels of Western nations in the protection of their nationals and their commercial interests at the treaty ports upriver. As early as 1897, at Shanghai, the navy had put these small forces ashore, ostensibly to quell some disturbance or meet some threat to Japanese lives and property. Rikusentai had been among the first units ashore in the Russo-Japanese War, had been used in the occupation of the German-held islands in Micronesia, and had spearheaded the Japanese intervention at Vladivostok in 1918. But the naval landing parties were used most extensively in China, where they often performed garrison duty after securing a particular landing site. Notably, such a unit had formed a permanent garrison just outside the Japanese quarter of the International Settlement at Shanghai, beginning in 1927. In its weaponry, equipment, and combat skills, however, the unit could hardly be considered a formidable amphibious force.

Until World War I, the Japanese army had hardly thought about the problems of amphibious warfare. But the Allied disaster at Gallipoli, demonstrating the difficulty of landings on a well-defended coast, had changed the army’s outlook sharply. Concluding that its future landings—in the Philippines and elsewhere— might have to be made in the face of enemy fire, the army began to insist on a more prominent role in amphibious planning. For that reason, the army actively joined the navy in a series of exercises in amphibious warfare during the 1920s: on the Shikoku coast in 1922, at Ise Bay in 1925, at Niijima in the Izu Islands in 1926 (where the army tried out its first amphibious tank), and along the Wakayama coast in 1929. In these maneuvers, both services worked out problems of navy gunfire support, maps for joint bombardments, ship-to-shore communications and control, various kinds of landing craft, assaults by divisionsized forces, the use of smoke shells, and the movement of troops over long stretches of water. From the experience gained in these maneuvers, the army and navy together developed a series of guidelines for amphibious operations. Among these, the Tairiku sakusen koyo (Outline of amphibious operations) of 1932 became the permanent manual on the subject. The result of five years of inter-service deliberations, the document clearly set forth principles for army-navy cooperation in amphibious operations and delineated the responsibility of commanders at various levels.

The eruption of fighting at Shanghai in 1932 brought about a shift in the relative attention and effort devoted to amphibious operations by the two armed services. In February, the permanent Japanese naval landing party clashed with Nationalist forces in the city streets and was badly bloodied in the process. Fearing that its garrison would be overrun, the navy called for army help in turning back the enemy. Although a mixed brigade was successfully landed to relieve the beleaguered landing party, the experience left much to be desired from the army’s point of view. The first landings were made in navy vessels unequipped with armor or armament and carrying inadequate amounts of ammunition and weapons.

The mediocre performance of the navy in the fighting at Shanghai in 1932 caused the navy to modify the way in which its naval landing parties were organized, armed, and employed. It was now perfectly willing to leave the development of a major amphibious capability to the army, including the design of docking ships, transports, and landing vessels. But in its determination to reduce its traditional reliance on the formation of ad hoc landing parties from warships on station, a measure which only depleted their complements and reduced their efficiency, the navy now decided to create permanent, specialized landing forces for limited, small-scale missions. Thus was born the Special Naval Landing Force, initially of battalion strength and armed with no more than small arms and mortars, but extensively trained in landing operations. Five units were formed in the 1930s, one at Shanghai and one each at the navy’s principal bases in the home islands: Yokosuka, Kure, Sasebo, and Maizuru. Each domestically based unit was designed to be embarked on warships, usually light cruisers or destroyers, whose naval guns could support the limited, specialized missions projected by the navy.

The army’s dissatisfaction with its actions at Shanghai also led it to rethink its dependence on the navy for amphibious operations. As a first step, it sought navy assistance in the development of a specialized landing ship. The Shinshu-maru, designed and built by the navy to army specifications, was the first ship of any nation specifically conceived for amphibious operations, a prototype of the landing ship dock later developed by the U.S. Navy. The army also went on to develop landing craft for tanks and to upgrade the training of several divisions specially earmarked for amphibious operations. Through these developments, the army became the dominant partner in the conduct of amphibious warfare even as the navy’s role shrank to providing gunfire support and convoying army landing craft to the beaches. Still, both services continued to cooperate in perfecting amphibious training and tactics.

Such training proved its worth when Japan’s China War broke out in 1937. The first amphibious operation of that conflict, in August, at the mouth of the Yangtze, reverted to the earlier arrangement of navy-directed landings in which the navy used its warships to bring the army’s troops ashore. But larger army forces were landed by army vessels, including the Shinshu-maru, in a textbook operation that followed the principles set down in the “Outline of amphibious operations”: a landing unopposed, at dawn, and at several places simultaneously. Three other major landings involving divisional forces took place over the next fourteen months: at Hangchow Bay in November 1937; at Ta-ya Wan (Bias Bay) near Hong Kong in October 1938; and at Bocca Tigris (Humen) at the entrance to the Pearl River the same month. All followed the essential pattern of established Japanese amphibious doctrine.

The Japanese landings in the China War provided excellent experience in working out the procedural and logistical problems of large-scale amphibious operations. While these operations, unopposed as they were, hardly put a strain on Japanese amphibious resources, in the words of a recent comparative study, they demonstrated that in amphibious warfare, “Japan entered World War II as well prepared as the United States, both in terms of operational forces and published doctrine.”

As discussed, in the 1930s the army had come to dominate the development of Japanese amphibious warfare, particularly in transport, equipment, strategic decisions, and the scale of forces directly involved. Yet, the army’s major missions were the defeat of enemy ground forces and the occupation of large land masses. For this reason, the army never saw its amphibious function as paramount. The same could be said of the navy, because of its obsession with the decisive battle at sea. The navy, however, confronted with the problems of seizing British and American island possessions in the Pacific, continued to manifest a strong interest in improving its amphibious capability.

Thus, as the likelihood of a war in the Pacific approached, the navy began to enlarge, strengthen, and diversify both its landing forces and their missions. The special naval landing forces grew to enlarged battalions of about two thousand men, equipped not only with small arms but also with heavy weapons, including 3-inch naval guns and howitzers. After the outbreak of the war, the battalions were sometimes enlarged by combining two or more such units into a new type of organization designated the Combined Special Naval Landing Force. On the eve of the Pacific War, some officers were inspired to promote a powerful and semi-independent amphibian force, but the idea never received much interest from the navy brass, caught up as they were in the strengthening of the battle line. Other proposals for extending the navy’s power ashore were realized, however, chief among them the idea of vertical envelopment. The navy had recognized the possibilities of this new dimension of warfare after the German paratroop successes in Europe in 1940. Late that year, under the cover designation of “Experiment 1001,” the Japanese navy began secret paratroop training for men selected from its special naval landing forces, and by the outbreak of the war had organized at least two paratroop units within those forces. The forces performed superbly in several combined operations that contributed to the rapid conquest of the Netherlands East Indies in the first months of the Pacific War.

On the eve of the Pacific War, therefore, Japan had good reason to be supremely confident of its abilities to conduct amphibious operations. This confidence was basic to its strategic decision to give military reality to the long-standing concept of nanshin, the southward thrust of Japanese power into Southeast Asia. Indeed, the first months of the Pacific War demonstrated how effectively the nation’s armed services had mastered the logistical and doctrinal problems of amphibious operations. Japanese landings in Southeast Asia—often at night, by forces that landed separately but concentrated at the point of attack—were carried out with a speed, surprise, and economy of force that sowed confusion and consequent demoralization among their British, Dutch, and American enemies. In these operations, the navy’s role was slighter than the army’s, but the former’s powerful covering forces, both distant and close, as well as its destruction of enemy air opposition, were necessary if not sufficient causes for the operations’ success.

With the end of the major Japanese offensives in the Pacific, however, the mission of the navy’s land forces changed from mobile to positional warfare. Indeed, the precedent for the shift had been set as early as 1939, with the Japanese occupation of Hainan Island, off the South China coast. Its seizure had been largely a navy operation, and with its completion, the special naval landing forces involved had been transformed into a naval guard force whose mission was defense and internal security. With the occupation of an expanded circle of island territories in the central and southwestern Pacific early in the war, the navy was obliged to repeat this model. Its land forces were increasingly given defensive missions, and their organization was changed accordingly. Increasingly, the shipborne, quickstrike special naval landing forces were replaced with konkyochitai (base forces) and their subordinate keibitai (guard units), often hastily organized and hastily dispatched to defend the navy’s advanced bases in the Pacific. Although some of these proved exceedingly resistant to attack, most were eventually annihilated by American amphibious offensives more powerful than any similar operations that Japan had ever mounted, or were simply bypassed and, by their isolation, rendered ineffective.

Clearly, then, the particular skill mastered by the Japanese navy in projecting its power ashore was the ability to make unopposed amphibious landings—operations carried out against undefended or lightly defended coastlines. This facility was amply manifested in all Japan’s modern wars. In these conflicts the navy, as well as the army, demonstrated mastery of the complex tactical and logistical problem of putting troops ashore in landings marked by stealth, deception, and dispersal.

What the navy never developed was a capability in amphibious assault. This term means the ability, such as that developed by the U.S. Marine Corps, to make an amphibious landing in the teeth of determined resistance by an alerted, fortified, and entrenched enemy. Indeed, the navy’s one experience in such operations, the assault on Wake Island in December 1941, met with near disaster and revealed how unprepared were Japan’s armed services to undertake them.

One must recognize, however, that for the entire history of the Japanese navy, amphibious assault was irrelevant. From the Sino-Japanese War of 1894-95 through the first year of the Pacific War, the navy had no need of such a capability. By 1943, even had Japan’s armed services developed the doctrine, training, forces, and techniques to conduct amphibious assault, its inability to establish local sea and air control in contested areas of the Pacific would have made such operations impossible.