A year after Japan's occupation of Kiska and Attu, U.S. troops invaded Attu on May 11, 1943 and successfully retook the island after three weeks of fighting, killing 2,351 Japanese combatants and taking only 28 as prisoners of war at the cost of 549 lives. Three months later on August 15, U.S. and Canadian forces landed on Kiska expecting the same resistance like Attu; they later found the entire island empty, as most of the Japanese forces secretly evacuated weeks before the landing. In spite of enemy absence on the island, over 313 Allied casualties were sustained nonetheless through car accidents, booby traps, landmines, and friendly fire, in which 28 Americans and four Canadians were killed in the exchange of fire between the two forces.