Lesson 3: The United States at War

Lesson Focus

Following the attack on Pearl Harbor, a unified America entered World War II. This lesson explores how the U.S. fought a two-front war in Europe and Asia, forged critical alliances, and laid the groundwork for postwar peace.

People to Know

Franklin Roosevelt, Dwight D. Eisenhower, Harry Truman

Learning Objectives

• Trace the course of World War II, analyzing key battles and strategic turning points in both the European and Pacific theaters.
• Explain the goals of the Atlantic Charter and the major agreements reached by Allied leaders at the critical Yalta Conference.

Japan's surprise attack on Pearl Harbor on December 7, 1941, devastated the U.S. Pacific fleet, causing President Franklin Roosevelt to declare it a “date which will live in infamy.”
This act ended American isolationism, uniting the country for war. After the U.S. declared war on Japan, Germany and Italy declared war on the U.S.
As a result, America was thrust into a global conflict, fighting the Axis powers on two fronts in Europe and Asia.

The Allies prioritized defeating Germany, adopting a “Europe First” strategy. This left the Soviet Union to face the Germans alone, leading to a desperate, heroic stand at Stalingrad in 1942-1943.
This battle became a major turning point on the Eastern Front. Meanwhile, American and British forces successfully drove Axis armies from North Africa.
This victory secured the Mediterranean and prepared the Allies for an invasion of Italy, weakening Germany from the south.

With the Axis weakened, the Allies launched the largest amphibious invasion in history on D-Day, June 6, 1944.
Under General Dwight D. Eisenhower, Allied forces landed in Normandy, France, and began pushing east. At the same time, the Soviet army advanced from the east, squeezing Germany between two fronts.
This combined pressure led to Germany's unconditional surrender on May 7, 1945, and the discovery of the horrific Nazi holocaust.

To defeat Japan in the Pacific, the U.S. adopted a strategy of “island hopping.”
This involved capturing key Japanese-held islands one by one to use as bases for the next attack. American forces faced brutal resistance on islands like Iwo Jima and Okinawa, where they encountered kamikaze pilots.
This deadly but successful strategy brought American forces closer to Japan, setting the stage for a final assault by the summer of 1945.

Fearing that a land invasion of Japan would cost a million American lives, President Harry Truman made a difficult choice.
After Japan refused to surrender, the U.S. dropped two atomic bombs: one on Hiroshima on August 6, 1945, and a second on Nagasaki. The unprecedented destruction forced Japan's emperor to surrender.
This act ended World War II on September 2, 1945, but it also introduced the world to the terrifying power of nuclear weapons.

To build a framework for peace, Allied leaders held several conferences during the war.
The Atlantic Charter (1941) established shared goals for a postwar world. At the Yalta Conference (1945), leaders planned the occupation of Germany and the creation of the United Nations.
Note that while these agreements aimed to ensure peace and stability, growing distrust between the Soviet Union and the West planted the seeds for the future Cold War.