Despite the U.S. declaring an “Open Door Policy” in support of China’s sovereignty, U.S. Marines on May 31, 1900 invaded China to help defeat the Boxer Rebellion. With imperial Great Britain, Germany, Austria-Hungary, France, Japan, and Russia trying to carve China into colonies, Secretary of State John Hay in the fall of 1899 declared the United States would honor an “Open Door Policy” that respected Chinese territorial and administrative integrity and allowed equal trading privileges for all nations. Nineteenth-century imperialists had forced China’s ruling Qing Dynasty to accept foreign dominance over much of China’s economic affairs. Two Opium Wars with...