Before the Russo-Japanese War, at the end of the 1800s, Japan manufactured the most prominent military vessels. They were heavily armed with thick armor protection. The Japanese intention to build these vessels should have been a clear sign to the worldwide nations that Japan was preparing for war. This was critical, especially for Russia. In 1904, the Japanese destroyed the superiority of the Russian navy in a single battle. The outcome of the battle of Port Arthur gave Japan not only an international status of strong military power but also a valuable experience and basis for the further development of its forces.

Japan’s navy won the Battle of Port Arthur because of its approach. It used highly concentrated, purposely built surprise-attack vessels. A small and agile concentrated fleet of torpedo boats devastated the Russian fleet. Japan gained confidence and maritime supremacy practically in a single battle. Nevertheless, the Russian navy was still operational and formidable. So, Japan finally ended all Russian naval capabilities in the Battle of Tsushima. Although it had a superior number of battleships, Russia suffered a heavy defeat by the overwhelming Japanese attack. Japan used a single concentrated combined force of destroyers, torpedo boats, and battleships.

This illustration depicts the Battle of Port Arthur during the Russo-Japanese War, where a Russian battleship is shown exploding from bombardment by Japanese battleships. On the right, a fleet of Japanese ships fires upon Russian battleships on the left in a surprise naval attack.
Japanese fleet bombards Russian ships at Port Arthur, Wikimedia Commons

Post-WWI Strategic Shift and the Influence of Mahan’s Theories

After World War I, Japan’s interests turned primarily toward control of East Asia. However, this was against the will of the British and the Americans. This prompted the Japanese to build up their naval approach. To prepare for an eventual conflict between Japan and the Western Allies. They were confident because throughout the years, starting with the Russo-Japanese War, Japan had mastered naval military operations. The growth of Japan’s Naval success and the roots of Japan’s World War II Naval doctrine were in the theories of Alfred Thayer Mahan.  

The Japanese navy officials studied the writings of Alfred Thayer Mahan. The theories explained the reasons for the British naval dominance in the world. It was logical for Japan to identify with Britain as they were both island nations. According to the writings, Britain became the world’s most powerful navy by preventing others from using its commercial shipping lines. Britain destroyed the enemy that threatened its commercial maritime lines in a single battle by deploying a large concentration of various military vessels. After the outcome, the British navy blocked the ports and established control over the defeated enemy. The concentration of various military vessels was the key to success. Japan developed “Kantai Kessen” also called “The Decisive Battle Doctrine” following these guidelines.

Reasons Behind Japan’s Adoption of “Kantai Kessen”

Following World War I, Japan gained previously German-controlled territory in China and various islands in the Pacific Ocean. Japan received the land as part of the South Seas Mandate. However, in the interwar period, Japan’s ambition increased and focused on more territories in Eastern Asia. After the end of the Anglo-Japanese alliance in 1922, Japan was no longer obligated to anyone. So, Japan’s ambitions caused tensions among the Western allies, and naturally, the Japanese military began to gradually prepare and fictionalize outcomes of conflict with the Western powers.

Map showing Japan’s territorial control before and during World War II, with areas marked for the furthest extent of control during the war, territories held by December 1941, regions under control by 1933, and the Japanese Mandate from 1919. Key locations in Asia and the Pacific, including China, the Soviet Union, Southeast Asia, and the Pacific islands, are labeled, with significant cities and bodies of water indicated. The map highlights Japan's expansive reach across the Pacific Ocean.
Map Depicting Japan’s Territories Prior to and During World War II, Cambridge University Press

The Japanese-controlled islands in the Pacific Ocean were in the strategic vicinity of territories controlled by the US. On the other hand, Japan’s desired land expansion in East and Southeast Asia was either under British control or bordering British-controlled territory. Japanese planners needed to develop an upgraded doctrine that would sustain the ability of the Japanese navy against the British and the US naval assets. The military planners considered the vast distances of the Pacific Ocean to their advantage. They estimated that the US Navy could not sustain itself in battles because of the enormous distance between the US mainland and battle-contested areas in the western Pacific. The long trips to re-supply or repair battle-damaged units would have limited the US’s capacity to engage in maritime battles. Therefore, Japanese military experts estimated that Japan would have been capable of defeating the US Navy in a single-decisive encounter.  

The Execution of the “Kantai Kessen”

Although the core of the doctrine was offensive, the principle of its execution relied on defensive tactical position. “Kantai Kessen” was most effective by luring or deceiving the enemy into a trap and destroying them by concentrated surprise attack. It produced excellent results when a combined fleet operated near land because it enabled fast recovery and re-supply for the units. However, when deployed in full offensive capability, it provided immense support to the ground troops of the Japanese army. The execution of the doctrine involved almost every military asset in a single battle, combining naval and air elements to achieve the objective, very similar to the German Blitzkrieg. From 1940 to 1942, the Japanese military achieved tremendous success, placing the Empire of Japan among the largest ones in the world.

Superior Firepower and Naval Dominance

Black and white photo of the battleship Yamato during its construction in September 1941. In the background to the right is the carrier Hosho, and at the top of the image is the store ship Mamiya. The shipyard is bustling with activity, and the surrounding landscape features mountains. This historical photograph is cataloged by the U.S. Naval Historical Center with the number NH 63433.
Construction of Yamato, September 1941, U.S. Naval Historical Center Photograph # NH 63433

“Kantai Kessen” acknowledged using superior naval guns and ships with better armor protection than the enemy. The main objective of the doctrine was to combine every available asset to increase the firepower to a level that would overwhelm the enemy. The development of superior naval guns was among the priorities of Japanese maritime production. For instance, the Japanese battleship Yamato was armed with nine 46 centimeters/45 Type 94 naval guns. The guns were the largest-caliber weapons ever mounted on a ship. Additionally, the Japanese Naval gun crews underwent extensive training procedures, and at the initial phase of the war, their performance was unmatched by any nation in the world.

Integration of Carriers and Advanced Air Power

Japan knew it could not match the US industrial power, so it compensated by producing higher-quality ships. To add on the firepower, the Japanese combined aircraft carriers that brought the effect of the “Kantai Kessen” to perfection. The formation of the 1st Air Fleet, better known as Kido Butai, brought the striking power of the doctrine to a maximum effect. Kido Butai consisted of combined weapon platforms capable of striking from sea, air, and undersea. At its peak, Kido Butai consisted of more than eight aircraft carriers, among which were the newest state-of-the-art carriers, Shōkaku and Zuikaku, seven battleships, fifteen cruisers, more than forty destroyers, among which were the deadliest Fubuki-class, and at least ten submarines. The air component provided by the aircraft carriers was at least four hundred planes-strong.

Historical black and white photo showing rows of Mitsubishi A6M2 Zero fighter aircraft lined up on the deck of the Imperial Japanese Navy aircraft carrier Shokaku, ready for the first strike wave against Pearl Harbor on December 7, 1941. The sea is visible in the background, indicating the carrier is at sea and poised for the imminent attack.
Aircraft Mitsubishi A6M2 Zero prepare to depart from the aircraft carrier Shokaku for the first wave of strikes at Pearl Harbor, December 7, 1941, Wikimedia Commons

At the start of the Pacific War, the Japanese aircraft carriers carried the most sophisticated and advanced aircraft in the world. Japan’s Naval Air Force operated the excellent fighter Mitsubishi A6M Zero. By the end of 1942, it had superior range, firepower, and climbing ability than every Allied plane in the Pacific. The Zero was feared most because of its outstanding maneuverability. Some allied fighters could not match it even in the later stage of the war. The aircraft carriers also carried tactical dive bombers and torpedo bombers. Aichi D3A was among the best dive-bombers in the world, highlighted by its precision. On the other hand, the Nakajima B5N was among the sturdiest torpedo bombers of its time. It was stable and capable of carrying one torpedo or at least 800 kilograms of bombs.

Effectiveness of the “Kantai Kessen” Doctrine

Since the start of the Second Sino-Japanese War in 1937, Japan effectively tested the “Kantai Kessen” doctrine and started to develop it even further. In 1941 and early 1942, Japan launched a series of offensives unmatched in speed and technical ability. They used combined forces, including destroyers, cruisers, aircraft carriers, and planes, in coordination with the ground forces. As such was the Battle of Rabaul. The Japanese overwhelmed the enemy’s garrison by using combined arms tactics. They coordinated the actions of the amphibious infantry, naval gunfire, and heavy air support from the carriers. It was the Pacific Blitzkrieg generated by Japan.

At Rabaul, the Allies’ coastal artillery batteries were demolished by over 90 Japanese planes. Soon after, the Japanese dispatched a marine commando force of more than 3,000 soldiers to clear the landing location. The landing force was heavily supported by naval gunfire from the Japanese cruisers and destroyers. After the cleaning operation, Japan sent the main landing force consisting of at least 4500 soldiers. In less than three weeks, the Japanese prevailed and fortified the strategically important township of Rabaul.

Limitations of the “Kantai Kessen” Doctrine

The implementation of “Kantai Kessen” didn’t stop at Rabaul. The Japanese also applied it in the Battle of Darwin and in their attempt to destroy the British Eastern Fleet. However, the doctrine had a few weaknesses. The striking force was vulnerable when discovered in the moments before the offensive. The aircraft on the carriers were easy targets because they were armed for ground operations, and the troops of the landing force had limited anti-air defenses. In those situations, the Japanese were at risk of being surprised and outmaneuvered. If the strike force’s distance between the objective and friendly controlled land territory was too long, the effect of the doctrine was unguaranteed.

Aerial black and white photograph of the Japanese attack on Pearl Harbor from the perspective of the attackers on December 7, 1941. Smoke billows from Pearl Harbor, T.H., caught off guard during the aerial onslaught. The USS West Virginia is engulfed in flames amidst the chaos of the surprise assault. This image is a captured Japanese photograph from the historic event.
Japanese-captured photo of the surprise Pearl Harbor attack, December 7, 1941, with USS West Virginia ablaze, Wikimedia Commons

Such an example was Pearl Harbor. Before the attack, some officers among the Japanese planners were partly skeptical of the operation’s success. Using only aircraft to defeat the enemy in a single battle was untested and unreliable. The “Kantai Kessen” called for the combined use of naval and ground assets whenever possible. The outcome of Pearl Harbor was devastating for the Americans but fatal for the Japanese. Perhaps if the Japanese forces used combined units, the operation would have been a success. However, by many military experts, that was doubtful because no one had the industrial potential the US had in the 40s. Nevertheless, the “Kantai Kesen” proved a valuable tactical and strategic lesson. It presented a basis for modern doctrines involving naval and maritime units. Later in the war, the US Navy based its vessel construction and Navy tactics on the experience of fighting the “Kantai Kessen.”