Japan participated in World War I from 1914 to 1918 as a member of the Allies/Entente and played an important role against the Imperial German Navy. Politically, the Japanese Empire seized the opportunity to expand its sphere of influence in China, and to gain recognition as a great power in postwar geopolitics.
Japan's military, taking advantage of the great distances and Imperial Germany's preoccupation with the war in Europe, seized German possessions in the Pacific and East Asia, but there was no large-scale mobilization of the economy. Foreign Minister Katō Takaaki and Prime Minister Ōkuma Shigenobu wanted to use the opportunity to expand Japanese influence in China. They enlisted Sun Yat-sen (1866–1925), then in exile in Japan, but they had little success.