Education About Asia

From the Nisshin to the Musashi: The Military Career of Admiral Yamamoto Isoroku

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On the morning of December 7, 1941, Imperial Japanese Navy (IJN) aircraft set out on one of the most famous operations in military history: a surprise air attack on the US naval base at Pearl Harbor, Hawai`i. The attack was devised and fashioned by Admiral Yamamoto, whose entire military career seems to have been leading to this very moment. Yamamoto was a naval officer who appreciated and understood the strategic and technological advantages of naval aviation. This essay will explore Yamamoto’s military career in the context of Imperial Japan’s aggressive expansion into Asia beginning in the 1890s and abruptly ending with Japan’s formal surrender on September 2, 1945, to the US and its Allies.

Early Career (1904–1922)

Yamamoto Isoroku was born in 1884 to a samurai family. Early in life, the boy, thanks to missionaries, was exposed to American and Western culture. In 1901, he passed the Imperial Naval Academy entrance exams with the objective of becoming a naval officer. Yamamoto genuinely respected the West—an attitude not shared by his academy peers. The IJN was significantly influenced by the British Royal Navy (RN), but for utilitarian reasons: mastery of technology, strategy, and tactics. Japanese military disdain for the West was probably because France, Germany, and Russia successfully demanded that Japan return to China a strategic peninsula in southern Manchuria it had seized after its victory in the 1894–1895 Sino-Japanese War. Despite allegations he was pro-Western, Yamamoto worked hard to understand Western technological, political, and military superiority.

Yamamoto graduated in spring 1904 and was appointed gunnery specialist. He was soon on the cruiser Nisshin, fighting in the Russo-Japanese War, and was a combatant in the decisive naval battle of the Tsushima Straits, where he was seriouslywounded but retained command of his ship’s cannon batteries. Officially commended for bravery, Yamamoto began his ascent through naval ranks.

In 1913, Yamamoto entered the Naval Staff College, a prerequisite for IJN promotion. Upon graduation, he received further promotions, and by 1919, Lieutenant Commander Yamamoto was sent to study at Harvard. Japanese officers in the West were expected to bring back information on their host countries, so Yamamoto spent much of his free time touring the US and studying its industry and resources, especially oil. He quickly realized that Japan’s lack of resources, raw materials, and a vast industrial complex would be grave disadvantages if war occurred with the US.

Meanwhile in Japan, a fundamental debate on geopolitical strategy had begun in reaction to the 1922 Washington Naval Conference and ensuing Five-Power Treaty, which limited Japan’s Naval power relative to the USN and RN. The dominant IJN and Imperial Army view was that Japan must always be prepared for a war against the West. Japan was responsible for delivering the peoples of Asia from Western oppression, and Imperial territorial expansion was a prerequisite. Yamamoto favored a different strategy; a US war would be a dire mistake and Japan should work for international collaboration and to end imperialism. This debate culminated with civilians and proponents of international collaboration losing control of the nation.


1. See, for instance, Edwin P. Hoyt, Three Military Leaders: Heihachiro Togo, Isoroku Yamamoto, Tomoyuki Yamashita (Tokyo: Kodansha International, 1993), 90.

2. For a review of Japanese operations during the first six months of the war, see Haruo Tohmatsu and H.P. Willmott, A Gathering Darkness: The Coming of War to the Far East and the Pacific, 1921–1942 (London: SR Books, 2004), 105–138.