Britain and the U.S. began the campaign against Germany with an invasion of North Africa in late 1942, winning decisively in May 1943. Meanwhile, the United States won a decisive victory over Japan in the Battle of Midway and began a campaign of island hopping in the Pacific Ocean. In 1943, the Allies launched an invasion of Italy and continued to pursue the island-hopping strategy. The major Allied leaders met at the Tehran Conference in 1943, where they began to discuss post-war plans. Among the concepts discussed was the United Nations, an intergovernmental organization championed by Roosevelt that would replace the League of Nations after the war. In 1944, the U.S. launched a successful invasion of northern France and won a decisive naval victory over Japan in the Battle of Leyte Gulf. By the time of Roosevelt's death in April 1945, the U.S. had occupied portions of Germany and was in the process of capturing Okinawa. That island was needed to begin all-out bombing of Japan. Germany and Japan would both surrender within six months of Roosevelt's death.