Answer: After Japan aligned itself with Britain in 1900
Explanation:
Germany and Japan became enemies in World War I. Japan declared war on the German Empire in 1914 and seized key German possessions in China and the Pacific.
As part of the post-war settlement at Versailles, Japan was given control of the Pacific Islands formerly under German rule, and allowed to maintain its hold on Shantung, at least until Chinese sovereignty was restored in 1922.
