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Military history of the United States during World War II

The military history of the United States during World War II covers the nation's role as one of the major Allies in their victory over the Axis Powers. The United States is generally considered to have entered the conflict with the 7 December 1941 surprise attack on Pearl Harbor by the Empire of Japan and exited it with the 2 September 1945 surrender of Japan. During the first two years of World War II, the US maintained formal neutrality, which was officially announced in the Quarantine Speech delivered by US President Franklin D. Roosevelt in 1937. While officially neutral, the US supplied Britain, the Soviet Union, and China with war materiel through the Lend-Lease Act signed into law on 11 March 1941, and deployed the US military to replace the British forces stationed in Iceland. Following the 4 September 1941 Greer incident involving a German submarine, Roosevelt publicly confirmed a "shoot on sight" order on 11 September, effectively declaring naval war on Germany and Italy in the Battle of the Atlantic.[1] In the Pacific Theater, there was unofficial early US combat activity such as the Flying Tigers.

During the war, some 16,112,566 Americans served in the United States Armed Forces, with 291,557 killed and 671,278 wounded.[2] There were also 130,201 American prisoners of war, of whom 116,129 returned home after the war.[3] Key civilian advisors to President Roosevelt included Secretary of War Henry L. Stimson, who mobilized the nation's industries and induction centers to supply the Army, commanded by General George Marshall and the Army Air Forces under General Hap Arnold. The Navy, led by Secretary of the Navy Frank Knox and Admiral Ernest King, proved more autonomous. Overall priorities were set by Roosevelt and the Joint Chiefs of Staff, chaired by William Leahy. The defeat of the Nazis was the US's official highest priority per its agreement with Britain; however, in practice, the US devoted more resources to the Pacific than Europe and Africa until 1944.


Admiral King put Admiral Chester W. Nimitz, based in Hawaii, in charge of the Pacific War against Japan. The Imperial Japanese Navy had the advantage, taking the Philippines as well as British and Dutch possessions, and threatening Australia but in June 1942, its main carriers were sunk during the Battle of Midway, and the Americans seized the initiative. The Pacific War became one of island hopping, so as to move air bases closer and closer to Japan. The Army, based in Australia under General Douglas MacArthur, steadily advanced across New Guinea to the Philippines, with plans to invade the Japanese home islands in late 1945. With its merchant fleet sunk by American submarines, Japan ran short of aviation gasoline and fuel oil, as the US Navy in June 1944 captured islands within bombing range of the Japanese home islands. Strategic bombing directed by General Curtis Lemay destroyed all the major Japanese cities, as the US captured Okinawa after heavy losses in spring 1945. With the atomic bombings of Hiroshima and Nagasaki, the Soviet invasion of Manchuria, and the imminent invasion of the home islands, Japan surrendered.


The war in Europe involved aid to Britain, its allies, and the Soviet Union, with the US supplying munitions until it could ready an invasion force. US forces were first tested to a limited degree in the North African Campaign and then employed more significantly with the British Forces in Italy in 1943–45, where US forces, representing about a third of the Allied forces deployed, bogged down after Italy surrendered and the Germans took over. Finally, the main invasion of France took place in June 1944, under General Dwight D. Eisenhower. Meanwhile, the US Army Air Forces and the British Royal Air Force engaged in the area bombardment of German cities and systematically targeted German transportation links and synthetic oil plants, as it knocked out what was left of the Luftwaffe post Battle of Britain in 1945. Being invaded from all sides, it became clear that Germany would lose the war. Berlin fell to the Soviets in May 1945, and with Adolf Hitler dead, the Germans surrendered.


The American victorious military effort was strongly supported by civilians on the home front, who provided the military personnel, the munitions, the money, and the morale to fight the war to victory. World War II cost the United States an estimated $296 billion in 1945 dollars, and at their highest in 1945, military expenditures comprised 38% of the national GDP.[4]

December 7, 1941 – , a surprise attack that killed almost 2,500 people in the then incorporated territory of Hawaii which caused the U.S. to enter the war the next day.

Attack on Pearl Harbor

January–August 1942 – , German U-boats engaged American ships off the U.S. East Coast.

Second Happy Time

February 23, 1942 – , a Japanese submarine attack on California.

Bombardment of Ellwood

by Japanese submarines

Attacks on California ships

March 4, 1942 – , a Japanese reconnaissance over Pearl Harbor following the attack on December 7, 1941.

Operation K

June 3, 1942 – August 15, 1943 – , the battle for the then incorporated territory of Alaska.

Aleutian Islands Campaign

June 21–22, 1942 – , the second attack on a U.S. military base in the continental U.S. in World War II.

Bombardment of Fort Stevens

September 9, 1942, and September 29, 1942 – , the only attack by enemy aircraft on the contiguous U.S. and the second enemy aircraft attack on the U.S. continent in World War II.

Lookout Air Raids

November 1944–April 1945 – , over 9,300 of them were launched by Japan across the Pacific Ocean towards the U.S. to start forest fires. On May 5, 1945, six U.S. civilians were killed in Oregon when they stumbled upon a bomb and it exploded, the only deaths to occur in the U.S. as a result of an enemy balloon attack during World War II.

Fu-Go balloon bombs

Although the Axis powers never launched a full-scale invasion of the United States, there were attacks and acts of sabotage on U.S. soil.

Amerika Bomber

Project Z

Operation PX

Cactus Air Force

Devil's Brigade (1st Special Service Force)

Eagle Squadron

Flying Tigers

Merrill's Marauders

Office of Strategic Services

Tuskegee Airmen

Allied war crimes during World War II

Diplomatic history of World War II

Equipment losses in World War II

Ethnic minorities in the U.S. armed forces during World War II

Foreign policy of the Franklin D. Roosevelt administration

Foreign policy of the United States

Greatest Generation

History of the United States

List of Medal of Honor recipients for World War II

Military history of the United States

Nazi foreign policy debate

United States and the Holocaust

United States casualties of war

United States home front during World War II

United States war crimes

World War II casualties

US Naval Advance Bases

Wallis and Futuna during the Second World War

Smith, Gaddis. American Diplomacy During the Second World War, 1941-1945 (1965)

online

from USHistory.com.

World War II

Oklahoma College of Law.

A Chronology of US Historical Documents

D-Day Museum.

The D-Day Story

Archived 22 June 2009 at the Wayback Machine, American Forces in Action Series. Washington, DC, United States Army Center of Military History 1994 (facsimile reprint of 1945). CMH Pub. 100-11.

Omaha Beachhead

US Congress. (from history.navy.mil)

Lend-Lease Act, 11 March 1941

The Ardennes: Battle of the Bulge Archived 13 November 2008 at the Wayback Machine. United States Army in World War II Series. Washington, D.C.: Office of the Chief of Military History, 1965.

Cole, Hugh M.