The United States could not fight all out in two theaters of war, so the decision was made — even before Pearl Harbor — to concentrate on first defeating Germany. Against Japan, the strategy that evolved during 1942 was to use Australia as a base of operations for retaking the Philippines and the south coast of China while defeating the Japanese fleet and capturing the islands in the Central Pacific. In Europe, America's entry into the war helped to revitalize the Allied forces. The Soviet Union pressed for the United States and Great Britain to open a second front with an Allied invasion of France as soon as possible, hoping a western front would force the Germans to redistribute their troops that were currently fighting against the USSR in the east. However, the British, remembering the heavy casualties in France during the First World War, were extremely reluctant to send their troops into Europe, and an invasion across the English Channel was postponed several times until June 1944. In the interim, British and American forces drove the Germans out of North Africa and invaded Sicily and Italy while Soviet troops pushed westward into Eastern Europe.
Naval war in the Pacific. In the days and weeks after Pearl Harbor, the Japanese invaded Malaya and captured Singapore, Guam, and Wake Island. Hong Kong was soon taken, and Japanese troops landed in the Philippines. When American forces on Bataan and Corregidor surrendered in the spring of 1942, General Douglas MacArthur left for Australia. Early in 1942, Japan also occupied the Dutch East Indies and Burma. Although U.S. bombers from the carrier Hornet did attack Tokyo (April 18, 1942), the famed Doolittle raid's primary purpose was to boost Allied moral; it did little damage. The key engagements early in the Pacific war took place at sea.
In May 1942, carrier‐based planes from the Japanese and American fleets met in the Battle of the Coral Sea. Although the American Navy suffered heavy losses, Japan's attempt to seize Port Moresby in southern New Guinea and cut off Australia failed. Less than a month later (June 3–6, 1942), Japan's attempt to take Midway Island was also thwarted. The Japanese lost four aircraft carriers and almost 300 planes in the Battle of Midway, which ended the threat to Hawaii. American troops went on the offensive in August 1942 with the invasion of the island of Guadalcanal in the Solomons. The intense fighting and naval engagements on and around Guadalcanal lasted until February 1943 when the Japanese, unable to land additional troops, abandoned the island.
Under MacArthur, American and Australian troops gained control of the northern coast of New Guinea by the end of 1943. The campaign in the Central Pacific then moved from the Gilbert to the Marshall to the Mariana Islands, which provided the bases from which the new American plane, the B‐29 Superfortress, began the systematic bombing of Japan in June 1944. MacArthur returned to the Philippines in October 1944, and what remained of the Japanese fleet was decisively beaten at the Battle of Leyte Gulf. By the spring of 1945, U.S. troops had captured Manila, the capital of the Philippines. The war in the Pacific, however, was far from over, and the Japanese fought harder as Allied forces moved closer to their home islands.
North Africa, Sicily, and the Italian campaign. Almost from the moment that Germany invaded the Soviet Union in June 1941, Russian leader Joseph Stalin demanded the opening of a western front to relieve pressure on his army, which was fighting the bulk of the enemy forces. Although the United States was willing to consider an offensive in Europe, the British were reluctant. Neither country was prepared to mount a major campaign in France in 1942, and they decided instead to invade North Africa. A combined Anglo‐American force commanded by General Dwight Eisenhower landed in Morocco and Algeria in November 1942. The inexperienced American troops suffered major setbacks, but by the spring of 1943, all of North Africa was under Allied control. While the fighting was still going on, Churchill and Roosevelt met in Morocco to discuss strategy. At the Casablanca Conference (January 1943), the leaders agreed that the war would continue until the “unconditional surrender” of Germany and Japan. While this decision was intended to calm Stalin's fears about Great Britain and the United States negotiating a separate treaty with the Axis powers, the cross‐Channel invasion was postponed again in favor of an attack against what Churchill called “the soft underbelly of Europe” — Sicily and Italy.
The Allied invasion of Sicily (July–August 1943) was a complete success, but securing Italy was another matter. Although Italian dictator Benito Mussolini had been overthrown (July 25), and Italy had surrendered (September 8), German troops still fought back. British and American forces took Naples less than a month after the initial landings at Salerno (September 1943), but difficult fighting during the winter of 1943‐44 brought them only within reach of Rome. Americans did not liberate Rome until June 4, 1944, just two days before the Normandy invasion. During the same period, the Russians inflicted a major defeat on the Germans in the Battle of Stalingrad (January 1943) and began to push west along the thousand‐mile eastern front.
The Teheran Conference and D‐Day. Churchill, Roosevelt, and Stalin, known as the Big Three, met for the first time at the Teheran Conference in November 1943. They agreed that the cross‐Channel invasion would take place in the following spring along with a Russian offensive in the east. This decision meant that while the British and American forces would control Western Europe, Soviet troops would liberate Eastern Europe and would probably remain in control there when the war ended. Stalin agreed that the Soviet Union would enter the war against Japan after Germany was defeated, a pledge the United States believed was critical to victory in the Pacific. The three leaders also discussed postwar Germany and the formation of a new international organization to replace the League of Nations but made no final decisions.
On D‐Day, June 6, 1944, the second front was finally opened when American, British, Canadian, and free‐French forces stormed the beaches of Normandy in Operation Overlord. Although there was stiff resistance at Omaha Beach, the invasion surprised the Germans, who expected the attack to come at the narrower Channel crossing near Pas de Calais. The Allied troops broke out of the Normandy beachhead in July and drove toward Paris, which was liberated in August. At the same time, the Allies launched another invasion of southern France. By September, the German army was driven out of France and Belgium, but the Allied advance stalled late in the year because of a lack of supplies. On the eastern front, Soviet forces were poised to move into Germany in late 1944.