Japan's Unofficial War with China - The Sino Japanese War 

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During the early twentieth century, the Imperial Japanese Army invaded and occupied Chinese lands without ever officially declaring war. In 1915, Japan issued the secret Twenty-One Demands to Chinese president Yuan Shikai, with the intent to claim economic and political power over China. The Demands were divided into five groups, with the Group Five demands including concessions similar to those Japan had forced on Korea. After twenty-five rounds of negotiations and intense political maneuvering on President Yuan’s part, the Twenty-One Demands were agreed to, except for the Group Five demands. The other Demands, though, reinforced Japanese control of southern Manchuria, Shandong, and eastern inner Mongolia. Japan’s hold on Manchuria was especially strong. The Chinese warlord Zhang Zuolin tolerated Japan’s encroachments on his Manchurian territory in exchange for their help maintaining his power, and Japan controlled southern Manchuria economically through its ownership of most of Manchuria’s railway lines and its lease of the Liaodong Peninsula.