On August 14, 1917, as World War I enters its fourth year, China abandons its neutrality and declares war on Germany.

From its inception, the Great War was by no means confined to the European continent; in the Far East, two rival nations, Japan and China, sought to find their own role in the great conflict. The ambitious Japan, an ally of Britain since 1902, wasted no time in entering the fray, declaring war on Germany on August 23, 1914 and immediately plotting to capture Tsingtao, the biggest German overseas naval base, located on the Shantung Peninsula in China, by amphibious assault. Some 60,000 Japanese troops, assisted by two British battalions, subsequently violated Chinese neutrality with an overland approach from the sea towards Tsingtao, capturing the naval base on November 7 when the German garrison surrendered. That January, Japan presented China with the so-called 21 Demands, which included the extension of direct Japanese control over most of Shantung, southern Manchuria and eastern Inner Mongolia and the seizure of more territory, including islands in the South Pacific controlled by Germany.

When China declared war on Germany on August 14, 1917, its major aim was to earn itself a place at the post-war bargaining table. Above all, China sought to regain control over the vital Shantung Peninsula and to reassert its strength before Japan, its most important adversary and rival for control in the region. At the Versailles Peace Conference following the armistice, Japan and China struggled bitterly to convince the Allied Supreme Council—dominated by the United States, France and Britain—of their respective claims on the Shantung Peninsula. A bargain was eventually struck in favor of Japan, who backed down from their demand for a racial-equality clause in the treaty in return for control over Germany’s considerable economic possessions in Shantung, including railways, mines and the port at Tsingtao.

Though Japan promised to return control of Shantung to China eventually—it did so in February 1922—the Chinese were deeply outraged by the Allied decision to favor Japan at Versailles. A huge demonstration was held in Tiananmen Square on May 4, 1919, protesting the peace treaty, which Chinese delegates in Versailles refused to sign. “When the news of the Paris Peace Conference finally reached us we were greatly shocked,” one Chinese student recalled. “We at once awoke to the fact that foreign nations were still selfish and militaristic and that they were all great liars.” A year after the peace conference closed, radical Chinese nationalists formed the Chinese Communist Party, which under the leadership of Mao Tse-tung and Chou En-lai, as well as many other former leaders of the anti-Versailles Treaty demonstrations, would go on to win power in China in 1949.