To placate Japan, Wilson promised to support the Japanese claims on the former German possessions in China and said that it would be Japan's reward for accepting the rejection of the proposal. Furthermore, over the advice of the United States Navy, Wilson also agreed to support Japanese claims to the Marianas, Marshall, and Caroline islands in the Pacific Ocean, which Japan had occupied in 1914, as mandates that Japan would administer on behalf of the League of Nations, instead of allowing the Japanese to annex the islands outright, as they had wanted. In May 1919, the peace conference formally decided that Japan would receive the Carolines, Marshall, and Marianas Islands as Class C League of Nations mandates. In the 1920s, the Japanese violated the terms of the mandates by preventing representatives of the League from visiting the islands, by bringing in settlers on the islands, and by building military bases, most notably at Truk, which became the main Japanese naval base in the Pacific. The Canadian historian Margaret Macmillan noted that some of the islands (most notably Truk, Tinian, and Saipan) that had been awarded to Japan in 1919 to be developed peacefully would become the scenes for famous battles in World War II.
