The Battle of Hong Kong (8–25 December 1941), also known as the Defence of Hong Kong and the Fall of Hong Kong, was one of the first battles of the Pacific campaign of World War II. On the same morning as the attack on the U.S. naval base at Pearl Harbor, forces of the Empire of Japan attacked British Hong Kong. The attack was in violation of international law as Japan had not declared war against the British Empire. Japan's unprovoked act of aggression was met with stiff resistance from Hong Kong's garrison, composed of local troops as well as British, Canadian and Indian units. Within a week the defenders abandoned the mainland, and less than two weeks later, with their position on the island untenable, the colony surrendered.