Japan's massive offensive to conquer Southeast Asia began to unfold 75 years ago this week. In territorial extent, it is among the largest, most successful series of military operations ever conducted. The Japanese offensive managed to destroy the front-line naval assets of two peer competitors, sinking seven capital ships without loss. It also managed to capture the greater portion of what is now ASEAN, the most economically dynamic region in the world. Although Japan would only hold the territory for four years, the offensive helped end formal colonialism in East Asia.

The advance

In the years prior to the opening of the Pacific War, Japan had already made significant territorial acquisitions. It came into possession of Formosa following the Sino-Japanese War, and Korea after the Russo-Japanese War. The League of Nations placed several Pacific island chains under Japanese control after World War I. In 1931 the Japanese Army seized Manchuria; in 1937, it began a war against China that would lead, by 1941, to the occupation of much of the north and east of the country, as well as several coastal enclaves. Finally, in 1941 Japan occupied French Indochina, giving it critical bases for the advance into the rest of the region.