Who Did the United States Fight in World War II?
The United States fought Japan, Germany, and Italy in World War II. Learn about the Axis Powers and America’s enemies in WWII.
Who did the United States fight in World War II? Japan, Germany, and Italy. These three nations formed the Axis Powers, the alliance that opposed the United States and its Allies (Britain, Soviet Union, China, France, and others) during World War II (1939-1945). The U.S. officially entered the war after Japan attacked Pearl Harbor on December 7, 1941, and Germany and Italy declared war on the U.S. days later.
For the citizenship test, you need to know the U.S. fought Japan, Germany, and Italy (or the Axis Powers) in World War II.
The Essential Facts
For the citizenship test, remember the U.S. fought:
Japan: Pacific theater; war started with Pearl Harbor attack
Germany: European theater; led by Adolf Hitler and the Nazis
Italy: European theater; led by Benito Mussolini
You can also answer: Axis Powers (the alliance of Japan, Germany, and Italy)
Any of these answers is correct for the test.
The Axis Powers
The three main enemies formed an alliance:
The Axis:
- Germany (Nazi Germany)
- Italy (Fascist Italy)
- Japan (Imperial Japan)
Why “Axis”:
The term came from a 1936 agreement between Germany and Italy creating a “Rome-Berlin Axis.” Japan joined later, forming the Tripartite Pact (1940).
Other Axis Members:
Several smaller nations allied with the Axis (Hungary, Romania, Bulgaria, etc.), but Japan, Germany, and Italy were the major powers.
Japan: Pacific Enemy
Why War with Japan:
Pearl Harbor (December 7, 1941):
Japan launched surprise attack on U.S. naval base at Pearl Harbor, Hawaii. About 2,400 Americans killed, much of Pacific Fleet damaged or destroyed. President Franklin Roosevelt called it “a date which will live in infamy.”
Japanese Expansion:
Japan had been conquering territories in Asia and the Pacific since the 1930s: China (1937), French Indochina, Philippines, etc. U.S. opposed Japanese aggression.
Oil Embargo:
U.S. embargoed oil and scrap metal to Japan (1941) to pressure Japan to stop expansion. Japan saw this as threat to survival and chose war.
Pacific War:
Major Battles:
- Coral Sea (May 1942)
- Midway (June 1942): Turning point
- Guadalcanal (1942-1943)
- Island hopping campaign (1943-1945)
- Iwo Jima and Okinawa (1945)
Atomic Bombs:
U.S. dropped atomic bombs on Hiroshima (August 6, 1945) and Nagasaki (August 9, 1945). Japan surrendered August 15, 1945.
Casualties:
About 111,600 Americans died in Pacific theater.
Germany: European Enemy
Why War with Germany:
Nazi Aggression:
Adolf Hitler’s Nazi Germany invaded Poland (September 1939), starting World War II in Europe. Germany conquered most of Europe by 1941.
Declaration of War:
After Pearl Harbor, Germany declared war on U.S. (December 11, 1941). Hitler honored alliance with Japan.
The Holocaust:
Nazi Germany was systematically murdering Jews and other groups. Six million Jews were killed in the Holocaust.
European War:
Major Events:
- U.S. entered war December 1941
- North Africa campaign (1942-1943)
- Italy invaded (1943)
- D-Day invasion of France (June 6, 1944)
- Battle of the Bulge (December 1944-January 1945)
- Germany invaded from west and east (Soviets from east)
German Surrender:
Germany surrendered May 8, 1945 (V-E Day). Hitler committed suicide April 30, 1945.
Casualties:
About 183,600 Americans died in European theater.
Italy: European Enemy
Why War with Italy:
Fascist Dictatorship:
Benito Mussolini led Fascist Italy, allied with Hitler’s Germany.
Declaration of War:
Italy declared war on U.S. (December 11, 1941), same day as Germany.
Italian Campaign:
Sicily (July-August 1943):
Allies invaded Sicily, first Allied territory in Europe.
Italian Mainland (September 1943):
Allies invaded Italy. Fighting continued until war’s end.
Italy’s Surrender (September 1943):
Italy surrendered to Allies, but Germany occupied northern Italy. Fighting continued against German forces.
Mussolini’s End:
Captured and executed by Italian partisans (April 1945).
Italy’s Role:
Italy was the weakest Axis power. After Italy’s surrender, it switched sides and fought with Allies.
The Allied Powers
The U.S. fought alongside the Allies:
Major Allies:
- Britain: Led by Winston Churchill
- Soviet Union: Led by Joseph Stalin; fought Germany on Eastern Front
- China: Fought Japan in Asia
- France: Occupied by Germany 1940-1944; Free French forces continued fighting
The Big Three:
Roosevelt (later Truman), Churchill, and Stalin led the Allied war effort and planned postwar world.
Alliance:
Strange alliance between democratic U.S./Britain and communist Soviet Union, united against fascism.
Why the U.S. Fought
Immediate Cause:
Pearl Harbor attack forced U.S. entry. Germany’s declaration of war brought U.S. into European war.
Broader Reasons:
- Stop Axis aggression and conquest
- Defend democracy against fascism and militarism
- Protect American interests and allies
- End Nazi atrocities (Holocaust)
- Preserve international order
Roosevelt’s Goals:
“Make the world safe for democracy,” defeat tyranny, create United Nations for peace.
How the War Ended
Germany:
- Surrendered May 8, 1945
- Hitler committed suicide
- Berlin captured by Soviets
- Germany occupied by Allies
Japan:
- Atomic bombs dropped August 1945
- Surrendered August 15, 1945 (V-J Day)
- Formal surrender ceremony September 2, 1945
- Emperor Hirohito remained but under U.S. occupation
Italy:
- Surrendered September 1943
- Switched to Allied side
- Mussolini executed April 1945
Consequences of WWII
For the Axis:
- Complete defeat and unconditional surrender
- Occupied by Allies
- War crimes trials (Nuremberg for Germans, Tokyo for Japanese)
- Democratic governments imposed
- Germany divided into East and West
For the World:
- About 70-85 million people died (military and civilian)
- United Nations created
- Cold War began between U.S. and Soviet Union
- U.S. became superpower
- Nuclear age began
- Decolonization of Asia and Africa
What to Memorize
For the citizenship test:
- Answer: Japan, Germany, and Italy (or Axis Powers)
- War dates: 1939-1945 (U.S. entered 1941)
- Pearl Harbor: December 7, 1941
- V-E Day: May 8, 1945 (Germany)
- V-J Day: August 15, 1945 (Japan)
If asked to elaborate:
“The United States fought Japan, Germany, and Italy in World War II. Japan attacked Pearl Harbor, bringing the U.S. into the war. The U.S. and its Allies defeated all three Axis powers.”
This is sufficient for the test.
Connections to Other Questions
This connects to:
- Question 80/42: FDR (President during WWII)
- Question 65/78: Wars in 1900s
- Question 43: Eisenhower (general in WWII)
Understanding WWII enemies explains why the war was fought and its global impact.
Top 10 Frequently Asked Questions
Who did the U.S. fight in WWII?
Japan, Germany, and Italy (the Axis Powers). This is the answer for the citizenship test.
Why did the U.S. fight Japan?
Japan attacked Pearl Harbor on December 7, 1941, killing about 2,400 Americans.
Why did the U.S. fight Germany?
Germany declared war on the U.S. on December 11, 1941, after Pearl Harbor. Germany was conquering Europe under Hitler.
Why did the U.S. fight Italy?
Italy declared war on the U.S. on December 11, 1941. Italy was allied with Germany under Mussolini.
Did the U.S. fight anyone else?
Minor Axis nations (Hungary, Romania, etc.), but Japan, Germany, and Italy were the main enemies.
Who were the Allies?
U.S., Britain, Soviet Union, China, France, and others fighting against the Axis.
How long did the war last?
1939-1945 in Europe/Asia; U.S. involved 1941-1945.
Which enemy was defeated first?
Italy (1943), then Germany (May 1945), then Japan (August 1945).
How many Americans died?
About 405,000 (183,600 in Europe, 111,600 in Pacific, 110,000 other).
What should I memorize for the citizenship test?
The U.S. fought Japan, Germany, and Italy in World War II. Know Pearl Harbor (December 7, 1941) brought U.S. into war. This is sufficient for the test.