The Americans did not bypass the small island of Iwo Jima because it wanted bases for fighter escorts; it was actually used as an emergency landing base for B-29s. The Japanese knew they could not win, but they devised a strategy to maximize American casualties. Learning from the Battle of Saipan they prepared many fortified positions on the island, including pillboxes and tunnels. The Marines attack began on 19 February 1945. Initially the Japanese put up no resistance, letting the Americans mass, creating more targets before the Americans took intense fire from Mount Suribachi and fought throughout the night until the hill was surrounded. Over the next 36 days, the Japanese were pressed into an ever-shrinking pocket, but they chose to fight on to the end, leaving only 1,000 of the original 21,000 defenders alive. The Marines suffered as well, suffering 25,000 casualties. The battle became iconic in America as the epitome of heroism in desperate hand-to-hand combat.