On January 18, 1915, Japan issues its Twenty-One Demands to the government of the Republic of China. Japan had previously established a significant degree of power and influence in the region through victory both the First Sino-Japanese War with China and the Russo-Japanese War with Russia, bringing Japan into the ranks of the Western imperial powers which were already exerting their power over China. Japan had also taken German possessions in China's Shandong province shortly after the war had started. Japan then quickly moved to exert more power in the region by issuing the Twenty-One Demands to China, a set of demands divided into five groups with the end goal to essentially place China under Japan's rule as a Japanese protectorate. The demands ranged for confirmation of Japanese possession of the former German holdings, extension of a lease to a railroad in Manchuria (Mongolia) held by Japan, to forbidding China from giving any further coastal or island concessions to foreign nations other than Japan. The most controversial of the demands were found in Group 5, which called for Japanese advisors to be placed in China's government, military, and economy, essentially giving Japan control over China.

The demands of Group 5 were eventually dropped and a revised version of the Twenty-One Demands were issued as an ultimatum to Chinese leader Yuan Shikai. Already dealing with warlords within China on top of the threat of a war with Japan and with the most damaging Group 5 demands removed, the Chinese government eventually agreed to the demands. However, Japan had gained little that it hadn't already possessed. Japan also drew the ire of the United States (which had pursued the Open Door Policy of leaving China open for all countries to trade) and Great Britain (who had been a close ally of Japan and also a major player in China and thus threatened by possibility of China becoming a Japanese protectorate). The Demands also led to further anti-Japanese sentiment as well as a growing nationalist movement in China.