USA

The military history of the United States in World War II covers the war against Germany, Italy, Japan, starting with the 7 December 1941 attack on Pearl Harbor. During the first two years of World War II, the United States had maintained formal neutrality while supplying Britain, the Soviet Union, and China with war material through the Lend-Lease Act which was signed into law on 11 March 1941, as well as deploying the U.S. military to replace the British invasion forces in Iceland.

U.S economic sanctions on Japan as part of the effort to deter Japanese military aggression in Asia and the Pacific outraged the Empire of Japan as the major cause of Japanese attack on Pearl Harbor. During the war, over 16 million Americans served in the United States Armed Forces, with 290,000 killed in action and 670,000 wounded.

Admiral Chester W. Nimitz was responsible for planning a series of some of the most famous naval battles in history. Japan’s main carriers were sunk during the Battle of Midway, and the Americans seized the initiative against the entrenched Japanese forces. The Pacific War became one of island hopping, moving air bases closer and closer to Japan. With its merchant fleet sunk, Japan ran short of aviation gasoline and fuel oil, as the U.S. Navy in June 1944 captured islands within bombing range of the Japanese home islands. Strategic bombing destroyed all the major Japanese cities, as the U.S. captured Okinawa after heavy losses in spring 1945. With the atomic bombings of Hiroshima and Nagasaki and an invasion and Soviet intervention imminent, Japan surrendered.

The war against Germany began with aid to Britain, her allies, and the Soviet Union, with the U.S. supplying munitions until it could ready an invasion force. The main invasion of France took place on June 6, 1944. Meanwhile, the U.S. Army Air Forces and the British Royal Air Force engaged in the area bombardment of German cities, systematically targeting German transportation links and synthetic oil plants, as it destroyed what was left of the Luftwaffe. With the Soviets unstoppable in the east, and the Allies unstoppable in the west, Germany was squeezed to death. Berlin fell to the Soviets in May 1945, and with Adolf Hitler dead, the Germans surrendered.

Soviet Union

The Soviet Union signed a non-aggression pact with Nazi Germany on 23 August 1939. In addition to stipulations of non-aggression, the treaty included a secret protocol that divided territories of Eastern Europe into German and Soviet “spheres of influence”, anticipating potential “territorial and political rearrangements” of these countries.

In 1940-41 Stalin ignored reports of an Axis invasion. On 22 June 1941, Hitler launched an invasion of the Soviet Union. Stalin was confident that the total Allied war machine would eventually stop Germany, and with Lend Lease from the West, the Soviets stopped the Wehrmacht some 30 kilometers from Moscow. Over the next four years, the Soviet Union repulsed Axis offensives, such as at the Battle of Stalingrad and Battle of Kursk, and pressed forward to victory in large Soviet offensives such as the Vistula-Oder Offensive. Stalin began to listen to his generals more after Kursk.

Stalin met with Winston Churchill and Franklin D. Roosevelt at the Tehran Conference and began to discuss a two-front war against Germany and future of Europe after the war. Berlin finally fell in April 1945, but Stalin was never fully convinced his nemesis Adolf Hitler had committed suicide. Fending off the German invasion and pressing to victory in the East required a tremendous sacrifice by the Soviet Union, which suffered the highest military casualties in the war, losing approximately 20 million men.

GERMANY

Under Hitler’s rule, Germany was transformed into a fascist state in which the Nazi Party took totalitarian control over nearly all aspects of life. The official name of the state was Deutsches Reich from 1933 to 1943 and Großdeutsches Reich (“Greater German Reich”) from 1943 to 1945. Nazi regime came to an end after the Allied Powers defeated Germany in May 1945, ending World War II in Europe.

Beginning in the late 1930s, Nazi Germany made increasingly aggressive territorial demands, threatening war if they were not met. Austria and Czechoslovakia fell in 1938 and 1939. Hitler made a non-aggression pact with Joseph Stalin and invaded Poland in September 1939, launching World War II in Europe. In alliance with Italy and smaller Axis powers, Germany conquered most of Europe by 1940 and threatened Great Britain. Reichskommissariats took control of conquered areas, and a German administration was established in what was left of Poland. Jews and others deemed undesirable were imprisoned, murdered in Nazi concentration camps and extermination camps, or shot.

After the German invasion of the Soviet Union in 1941, the tide gradually turned against the Nazis, who suffered major military defeats in 1943. Large-scale aerial bombing of Germany escalated in 1944, and the Axis powers were pushed back in Eastern and Southern Europe. Following the Allied invasion of France, Germany was conquered by the Soviet Union from the east and the other Allied powers from the west and capitulated within a year. Hitler’s refusal to admit defeat led to massive destruction of German infrastructure and additional war-related deaths in the closing months of the war.

GREAT BRITAIN

When the United Kingdom declared war on Nazi Germany at the outset of World War II, the British Empire was a global superpower, with direct or de facto political and economic control of 25% of the world’s population, and 30% of its land mass.

The contribution of the British Empire and Commonwealth in terms of manpower and materiel was critical to the Allied war effort. Close to 15 million serving men and women, fought across Europe, Africa, Asia, and in the Mediterranean Sea and the Atlantic, Indian, Pacific and Arctic Oceans. Commonwealth airforces fought the Luftwaffe to a standstill over Britain, and its armies fought and destroyed Italian forces in North and East Africa and occupied several overseas colonies of German-occupied European nations.

The Commonwealth defeated, held back or slowed the Axis powers for three years while mobilizing their globally integrated economy, military, and industrial infrastructure.These efforts came at the cost of 150,000 military deaths, 400,000 wounded, 100,000 prisoners, over 300,000 civilian deaths, and the loss of 70 major warships, 39 submarines, 3,500 aircraft, 1,100 tanks and 65,000 vehicles.

Britain became the nucleus of the Allied war effort in Europe. Canada delivered almost $4 billion in direct financial aid to the United Kingdom, while Australia and New Zealand began shifting to domestic production to provide material aid to US forces in the Pacific. Following the US entry into the war in December 1941, the Commonwealth and United States coordinated their military efforts and resources globally.

Japan

Having already terrorized and destroyed areas of mainland China before the push to take over other territories in Southeast Asia, Japan began a diplomatic campaign to secure allies. In September 1940, Germany, Italy, and Japan became allies under the Tripartite Pact. As Japan worked to increase its imports through economic agreements with French and Dutch colonies, the United States, Great Britain, and the Netherlands began embargo of gasoline, aviation gas, scrap metal, steel and other essential building materials.

After the Japanese attack on Pearl Harbor, the U.S., United Kingdom and other Allies declared war on Japan. The war spread throughout the Pacific region as Japan had initial success in its military campaign. However, in 1943 the hard-fought campaigns at the battles of Buna-Gona, the Tarawa, the Philippine Sea, Leyte Gulf, Iwo Jima, Okinawa, and others resulted in horrific casualties, mostly on the Japanese side, and produced further Japanese retreats.

On August 6 and August 9, 1945, the U.S. dropped two atomic bombs on Hiroshima and Nagasaki. An estimated 150,000–246,000 people died as a direct result of these two bombings, during which the Soviet Union entered the war against Japan. Japan surrendered on August 15, 1945, and a formal Instrument of Surrender was signed on September 2, 1945, on the battleship USS Missouri in Tokyo Bay. The surrender was accepted, from a Japanese delegation led by Mamoru Shigemitsu, by General Douglas MacArthur, as Supreme Allied Commander, along with representatives of each Allied nation.

Over the course of the war, Japan displayed many significant advances in military technology, strategy, and tactics. Among them were the Yamato-class battleship, the Sen-Toku submarine bomber carriers, the Mitsubishi Zero fighters, and Kamikaze bombers.