In 1915, the Japanese government insisted that Yuan Shikai accept a series of 21 demands that would have given Japan a virtual protectorate over the Chinese government and economy. Yuan was able to fend this off.
Japan received Germany's sphere of influence in the Shandong Province as a reward for its support of Allied cause in WWI. On hearing that, the Chinese government accepted the decision.
Patriotic students, supported by other sectors of the urban population, demonstrated in Beijing and other major cities of the country. Although this May 4th Movement did not lead to the restoration of Shandong, it did alert a substantial part of the politically literate population to the threat to national survival and the incompetence of the warlord government.
Consequence of a failed revolution of 1921
Two parties form an alliance to oppose the warlords and drive the imperialist powers out of China.