At the January 1943 Casablanca Conference, the U.S. and Britain agreed to defeat Axis forces in North Africa and then launch an invasion of Sicily after the North African campaign, with an attack on France to follow in 1944. At the conference, Roosevelt also announced that he would only accept the unconditional surrender of Germany, Japan, and Italy. The demand for unconditional surrender was calculated to reassure the Soviets, who were still insisting on an immediate attack on German-occupied France, that the United States would not seek a negotiated peace with Germany. In February 1943, the Soviet Union turned the tide on the eastern front by winning a decisive victory at the Battle of Stalingrad. The Allies launched an invasion of Sicily in July 1943, capturing the island by the end of the following month. During the campaign in Sicily, King Victor Emmanuel III of Italy arrested Mussolini and replaced him with Pietro Badoglio, who secretly negotiated a surrender with the Allies. Despite his earlier insistence on unconditional surrender, Roosevelt accepted armistice terms that allowed Badoglio to remain in power. Germany quickly restored Mussolini to power and set up a puppet state in northern Italy. The Allied invasion of mainland Italy commenced in September 1943, but the Italian Campaign moved slowly until 1945. Roosevelt consented to the campaign only on the condition that the British commit to an invasion of France in mid-1944, and the Allied Powers began to build up a force for that operation, diverting soldiers from the Italian Campaign.