On March 31, 1854, Commodore Matthew Perry and the "Black Ships" of the United States Navy forced the opening of Japan to the outside world with the Convention of Kanagawa. Subsequent similar treaties with the Western countries in the Bakumatsu period brought Japan into economic and political crises. The abundance of the prerogative and the resignation of the shogunate led to the Boshin War and the establishment of a centralized state unified under the name of the Emperor (Meiji Restoration). Adopting Western political, judicial and military institutions, the Cabinet organized the Privy Council, introduced the Meiji Constitution, and assembled the Imperial Diet. The Meiji Restoration transformed the Empire of Japan into an industrialized world power that embarked on a number of military conflicts to expand the nation's sphere of influence. After victories in the First Sino-Japanese War (1894?1895) and the Russo-Japanese War (1904?1905), Japan gained control of Taiwan, Korea, and the southern half of Sakhalin.

The early twentieth century saw a brief period of "Taisho democracy" overshadowed by the rise of expansionism and militarization. World War I enabled Japan, which joined the side of the victorious Allies, to expand its influence and territorial holdings. Japan continued its expansionist policy by occupying Manchuria in 1931. As a result of international condemnation for this occupation, Japan resigned from the League of Nations two years later. Japan introduced democracy to the newly acquired territories in response to Taiwanese public opinion.[30] In 1935, local assemblies were established in Taiwan.[30] In 1936, Japan signed the Anti-Comintern Pact with Nazi Germany, joining the Axis powers in 1941. In 1941, Japan signed the Soviet?Japanese Neutrality Pact with Soviet Union, respecting both Manchukou and Mongolian People's Republic territories.

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