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Fighting World War II

Fighting World War II

Author: Sophia Tutorial

Understand the strategies that the United States and the Allies used to defeat the Axis Powers during WWII

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what's covered
Despite the attack on Pearl Harbor and subsequent Japanese expansion in the Pacific, President Roosevelt and his military advisors viewed Nazi Germany as the greater threat. As a result, the United States adopted a “Europe First” strategy, in which America concentrated most of its resources and energies on defeating Germany. In the Pacific, the U.S. engaged in an “island hopping” campaign in which naval and ground forces moved from one island to the next across the Pacific, steadily advancing towards Japan.

This tutorial examines American military participation in World War II in three parts:

  1. Mobilizing an Army
  2. The War in Europe
  3. The War in the Pacific

1. Mobilizing an Army

Before the United States could enter combat in Europe or the Pacific, it needed to raise an army.

Before the attack on Pearl Harbor, Roosevelt’s administration recognized that the U.S. needed to prepare for war.


In September of 1940, Congress enacted a law that established the first peacetime draft in American history. Initial draftees were required to serve for one year, and the law stipulated that no more than 900,000 men could receive military training at a time.

Still, at the time of the attack on Pearl Harbor, the U.S. had only one division that was ready to be deployed overseas. Military planners estimated that as many as nine million men would be needed to fight the war. As a result, the the draft program was significantly expanded.


Over the course of the war, approximately 50 million men registered for the draft. 10 million were inducted into the armed services.

The American armed forces were overwhelmingly young and white during the war. Few of them had graduated from high school.

did you know
In 1944, the average age of an American soldier was 26 years old. Approximately four out of every ten white American soldiers had finished high school.

Approximately 2.5 million African Americans registered for the draft, and 1 million served in the military — in segregated units. Despite the performance of the Harlem Hellfighters and other black units during the First World War, military officials deemed African Americans unfit for combat at the outset of the war.

did you know
The U.S. Navy only accepted African Americans as cooks and stewards.

Most black units served as support troops during the war and rarely saw combat. However, as the war continued, black soldiers and sailors who served in combat did so with distinction.


The 99th Pursuit Squadron — African-American pilots who had trained at the Tuskegee Institute — escorted bombers on attack runs over North Africa, Italy, and Germany.

Approximately 44,000 Native Americans served in the armed forces during the war. In the Pacific, Navajo soldiers made a unique contribution as “code-talkers”. They exchanged information over radios using codes based on their native language, which the Japanese were unable to decipher.

did you know
A small number of Comanche code talkers performed a similar function for American armies in Europe.

Many Japanese Americans attempted to enlist when the war began, but draft boards usually classified them as “undesirable aliens”, unfit for service. As the war continued and the need for fighting men increased, military officials upgraded their eligibility status.

did you know
Before enlisting, Japanese American men were required to swear allegiance to the United States, even though there was no reason to question their loyalty. A few hundred men who refused to sign the oaths were imprisoned for resisting the draft.

Nearly 33,000 Japanese Americans served in the military during World War II.


The Japanese-American 442nd Regimental Combat Team, which experienced heavy fighting in Europe, finished the war as the most-decorated unit in U.S. military history.

Tens of thousands of American women also served in a variety of positions during the war. Approximately 350,000 women enlisted in the armed forces. They worked as nurses, drove trucks, repaired airplanes, and performed clerical work to make men available for combat.


Women who joined the Women’s Airforce Service Pilots (WASPs) flew planes from American factories to military bases.

did you know
Over 1,600 female nurses earned medals for courage under fire during World War II.

While the successes of these Americans were praised, the persistence of segregation, racial tension, and questioned loyalty indicated that the United States still struggled with social justice at home, as its armed forces battled the Axis Powers abroad.

2. The War in Europe

President Roosevelt was committed to ensuring the survival of Great Britain. However, at the end of 1941, he had yet to meet Soviet Premier Joseph Stalin, whose country was also enduring a brutal Nazi assault.

did you know
In June of 1941, Hitler broke his non-aggression pact with Stalin and invaded the Soviet Union.

When the U.S. entered the war, Nazi Germany seemed to be on the brink of conquering Europe. German forces were advancing towards major Soviet cities. German bombers and fighters regularly attached London. German submarines prowled the Atlantic, attacking U.S. supply ships.

Together, the leaders of the United States, the Soviet Union, and Great Britain — known as the Big Three — sought to work together to defeat Nazi Germany.

term to know
Big Three
The nickname given to the leaders of the three major Allied nations: Winston Churchill, Franklin Roosevelt, and Joseph Stalin

They did so despite their political differences. Stalin was suspicious of Churchill and Roosevelt and, although the President hoped he could build a good relationship with Stalin, he was equally suspicious of the Soviet leader.

Disagreements among the Big Three centered on the development of a “second front”, something Stalin desired, to relieve German pressure on the Soviet Union.

term to know
“Second Front”
Also known as the "western front", the Allied offensive launched in western Europe to force Hitler’s forces to fight the Allies in France as well as in the Soviet Union

Prime Minister Winston Churchill and President Roosevelt met several times during the war. The meeting pictured above took place in Casablanca, Morocco, in January of 1943.

To engage Nazi forces fighting in Europe, the U.S. sent troops to North Africa in 1942. British forces had been fighting German and Italian armies in the region since the summer of 1940. The arrival of American troops turned the tide of the war in the southern Mediterranean in favor of the Allies.

The Allied campaign in North Africa did nothing to draw German troops away from the Soviet Union, frustrating Stalin. Soviet armies fought alone against hundreds of German divisions in bitter, street-by-street battles in Stalingrad and Leningrad. Stalin pressured the U.S. and Great Britain to establish the “second front” by invading France from England, across the English Channel.

To Stalin’s dismay, Churchill convinced Roosevelt to delay an Allied invasion of France in favor of an invasion of Sicily and Italy. Churchill saw Italy as vulnerable, and believed that Italian support for Mussolini was waning. He pointed out that if Italy was taken out of the war, the Allies would control the Mediterranean. This was vital to Great Britain, which controlled Egypt in North Africa and oversaw governments in much of the Middle East, including Iraq.

The joint American-British campaign to take Sicily and Italy involved brutal combat. In late 1943, Mussolini’s government was overthrown by a popular uprising. Germany responded by sending more troops into the Italian peninsula. It was not until June of 1944 that Allied forces liberated Rome. Fighting in northern Italy continued into 1945.

The Italian campaign frustrated Stalin. He saw it as evidence that British interests took precedence in the Allied war effort. He also believed that it delayed an invasion of France, which meant that the Soviet Union would continue to bear the brunt of fighting against Nazis in the east.

did you know
Approximately 20 million Russians — soldiers and civilians — died during World War II.

During a meeting in Tehran, Iran, in November of 1943, Churchill, Roosevelt, and Stalin finalized plans for a cross-channel invasion of France. On June 6, 1944, known as D-Day, Stalin’s much-desired second front finally became a reality when Allied forces stormed the beaches of northern France.

term to know
June 6, 1944; the date of the invasion of Normandy, France, by Allied forces, which formally opened a second front in Europe

Beginning at 6:30 a.m., 24,000 British, Canadian, and American soldiers waded ashore along a 50-mile stretch of the Normandy coast. More than a million others would follow their lead. German forces were entrenched in concrete bunkers on the cliffs above. In addition to machine-gun and artillery fire, Allied soldiers encountered barbed wire and mines.

One of the most-reproduced photographs of D-Day, “Into the Jaws of Death” by Robert F. Sargent, shows American soldiers exiting a landing craft and wading ashore on an area of the Normandy coast designated “Omaha Beach” on the morning of D-Day.

The largest amphibious military operation in world history took place on D-Day. More than 10,000 Allied soldiers were wounded or killed during the assault. Although the invasion diverted German forces from eastern Europe, the Soviets had, by this time, turned back the German invaders at Stalingrad and Leningrad. Germany now faced Allied armies on its eastern and western flanks.

Another year of vicious fighting would pass before the war in Europe ended:

Date Event
August 20, 1944 — Paris, France, liberated from German occupation
December 16th, 1944-January 1945 — Germany attacked western Allied armies and launched a desperate offensive against American forces
— The subsequent Battle of the Bulge resulted in approximately 90,000 American casualties
— Germany no longer capable of mounting offensive operations against the Allies
April 1945 — Soviet forces reached Berlin
— American and British forces atacked Germany’s innermost defenses in the western part of the nation
— Hitler committed suicide on April 30th
May 8, 1945 — Germany surrendered: the war in Europe was over

3. The War in the Pacific

The war in the Pacific started badly for the United States and its allies. Following the attack on Pearl Harbor, Japanese forces won a series of victories in Southeast Asia and, by the spring of 1942, threatened Australia.


Japanese attacks on the Philippines in early 1942 forced the surrender of 78,000 American and Filipino soldiers. This was the largest surrender in American military history. The subsequent march to a prisoner-of-war camp, known as the “Bataan Death March”, resulted in the deaths of approximately 650 American and 10,000 Filipino prisoners.

The tide began to turn in favor of the Allies in mid-1942. In the Battle of the Coral Sea in May of 1942, the U.S. Navy turned back a Japanese force that intended to invade Australia. In June of 1942, the U.S. Navy delivered a devastating blow to the Japanese Navy during the Battle of Midway, destroying four of its six aircraft carriers.

Thereafter, the U.S. pursued a strategy of island hopping throughout the Pacific.

term to know
Island Hopping
American strategy in the Pacific during World War II; focused on capturing islands that were vital to Japanese communications and transportation

By attacking only those islands and other locations that would significantly disrupt the Japanese war effort, the island hopping strategy sought to advance American air power towards Japan. When it was close enough, Japan could be bombed in preparation for an amphibious invasion.

Moving from one island to the next, fighting in locations including Guadalcanal in the Solomon Islands and Saipan in the Marianas Islands, American naval, air, and land forces edged closer to Japan.

In the spring of 1945, battles on Iwo Jima and Okinawa, south of Japan, revealed the high cost of island hopping. Both islands were valuable as air bases. The U.S. could launch long-distance bombing raids on Tokyo and other major Japanese cities from both of them.

In February of 1945, American forces attacked Iwo Jima. They endured heavy shelling and machine gun fire from entrenched Japanese forces as they came ashore. Japanese soldiers refused to surrender, which made the fighting brutal and costly. By the end of the battle in late March of 1945, many Japanese and American lives had been lost. Only a few hundred Japanese soldiers had surrendered.

The invasion of Okinawa, which began in April of 1945, resulted in similar carnage by the time American forces captured the island in June of 1945:

Iwo Jima Okinawa
Japanese Deaths 20,000 soldiers 70,00 soldiers
10,000 civilians
American Deaths 6,000 marines 17,000 soldiers

The savagery of the fighting that American soldiers experienced on Iwo Jima and Okinawa, along with the extraordinary casualties, weighed heavily on the minds of military officials as they planned an amphibious invasion of the Japanese island of Kyushu, code-named Operation Olympic. The casualties that U.S. forces experienced while island hopping — and the serious losses that would result from an invasion of Japan — concerned President Harry S. Truman. He became President when Franklin D. Roosevelt died on April 12, 1945. It was up to him to decide how the United States would end the war in the Pacific.

In addition to organizing the economy to supply the “arsenal of democracy”, the United States mobilized an enormous number of men to fight in Europe and the Pacific. President Roosevelt adopted a “Europe First” strategy, in which the U.S. concentrated on defeating Nazi Germany. Deliberations over the opening of a second front in Europe exposed differences between the major Allied leaders. Despite their disagreements, the United States, Great Britain, and the Soviet Union turned the tide of the war and forced Germany to surrender in the spring of 1945. In the Pacific, the U.S. pursued a strategy of island hopping. As the cost of this strategy became clear during the summer of 1945, President Truman struggled with a decision that no other President had confronted.

This tutorial curated and/or authored by Matthew Pearce, Ph.D

Source: Into the Jaws of Death, June 6, 1944, Public Domain, Derived from Openstax tutorial 27.2 27.3 and 27.4 Some sections edited or removed for brevity.

Terms to Know
Big Three

the nickname given to the leaders of the three major Allied nations: Winston Churchill, Franklin Roosevelt, and Joseph Stalin.


June 6, 1944; the date of the invasion of Normandy, France, by Allied forces, which formally opened a second front in Europe.

island hopping

American strategy in the Pacific during World War II; focused on seizing key islands that were vital for Japanese communications and transportation.

“second front”

also known as the "western front," the Allied offensive launched in western Europe for the purpose of dividing Hitler’s armies between fighting the Allies in France and in the Soviet Union.

People to Know
Franklin Delano Roosevelt

democratic U.S president from 1933 until his death in 1945, who was elected for an unprecedented four terms; led the United States through the Great Depression and World War II; member of the Allied Powers’ “Big Three” leaders.

Harry S. Truman

democratic U.S president who took office after Franklin Roosevelt’s death in 1945 and remained in office until 1953; navigated the decision to drop the atomic bomb on Japan and the first years of the Cold War between the U.S. and the Soviet Union.

Joseph Stalin

leader of the Soviet Union from 1929-1953; member of the Allied Powers’ “Big Three” leaders.

Winston Churchill

Prime Minister of Great Britain from 1940-1945 who led his country through World War II; member of the Allied Powers’ “Big Three” leaders.