---
title: "Big Three — APUSH Definition, Conferences & Exam Guide"
description: "The Big Three were FDR, Churchill, and Stalin, the WWII Allied leaders whose cooperation won the war and whose disagreements at Yalta set up the Cold War."
canonical: "https://fiveable.me/apush/key-terms/big-three-leaders-of-the-us-soviet-union-and-great-britain"
type: "key-term"
subject: "AP US History"
unit: "Unit 7"
---

# Big Three — APUSH Definition, Conferences & Exam Guide

## Definition

The Big Three were the leaders of the major Allied powers in World War II: President Franklin D. Roosevelt (US), Prime Minister Winston Churchill (Great Britain), and Premier Joseph Stalin (Soviet Union), who coordinated strategy against the Axis and shaped the postwar world at conferences like Yalta.

## What It Is

The Big Three is shorthand for the three Allied leaders who ran the war against the [Axis powers](/apush/key-terms/axis-powers "fv-autolink"): Franklin D. Roosevelt of the United States, Winston Churchill of Great Britain, and Joseph Stalin of the Soviet Union. They met at a series of wartime conferences (most famously Tehran in 1943 and Yalta in February 1945) to coordinate military strategy, like the timing of the D-Day invasion, and to hammer out plans for the [postwar](/apush/unit-8/context-us-as-global-leader/study-guide/gQBcPKrfySmr9qtQziHd "fv-autolink") world, including the occupation of Germany and the creation of the United Nations.

Here's the thing that makes the Big Three more than a trivia answer. This was an alliance of convenience. The US and Britain were capitalist democracies; the USSR was a communist dictatorship. They cooperated because defeating Hitler required it, which is exactly what the CED means when it credits [Allied victory](/apush/unit-7/postwar-diplomacy/study-guide/xMjx3s8J0K11zGx6sHBP "fv-autolink") to "Allied cooperation." Once the common enemy was gone (and once FDR died in April 1945 and Truman took over), the cracks in that partnership became the opening fault lines of the Cold War.

## Why It Matters

The Big Three lives in **Topic 7.13 (World War II: Military)** in [Unit 7](/apush/unit-7 "fv-autolink") and supports learning objective **[APUSH](/apush "fv-autolink") 7.13.A**, which asks you to explain the causes and effects of Allied victory over the Axis. The essential knowledge for that objective names Allied cooperation as one of the core reasons the US and its allies won, and the Big Three is the human face of that cooperation. It also matters for the America in the World theme, because the wartime partnership between FDR, Churchill, and Stalin is the bridge between Unit 7 and Unit 8. The same three countries that fought together at Normandy were facing off across an Iron Curtain within two years, and you can't explain why the Cold War started without explaining what the Big Three agreed (and failed to agree) on at Yalta.

## Connections

### [Yalta Conference (Unit 7)](/apush/key-terms/yalta-conference)

Yalta in February 1945 was the Big Three's most consequential meeting. They divided Germany into occupation zones and [Stalin](/apush/key-terms/stalin "fv-autolink") promised free elections in Eastern Europe, a promise he broke. Yalta is where wartime cooperation starts turning into Cold War suspicion.

### Allied Powers (Unit 7)

The Big Three were the leaders; the Allied Powers were the nations they led, plus dozens of other countries fighting the Axis. Think of the Big Three as the steering committee of the larger Allied coalition.

### Atlantic Charter (Unit 7)

Before Stalin joined the picture, FDR and [Churchill](/apush/key-terms/churchill "fv-autolink") met in August 1941 (before the US even entered the war) and laid out shared goals like self-determination and free trade. The Atlantic Charter is the ideological blueprint the Big Three's later conferences kept circling back to.

### [Atomic Bomb (Units 7-8)](/apush/key-terms/atomic-bomb)

At Potsdam in July 1945, the Big Three lineup had changed (Truman replaced FDR), and Truman hinted to Stalin that the US had a powerful new weapon. The bomb ended WWII but also kicked off the nuclear arms race, making it the literal hand-off point between Unit 7 and [Unit 8](/apush/unit-8 "fv-autolink").

## On the AP Exam

On multiple choice, the Big Three usually shows up through a stimulus, like an excerpt from a Yalta agreement or a wartime photo of FDR, Churchill, and Stalin, with questions asking why the Allies won (Allied cooperation per APUSH 7.13.A) or how wartime decisions led to postwar tensions. No released FRQ has used the term "Big Three" verbatim, but the concept is gold for essays. A causation LEQ on the origins of the Cold War almost requires you to discuss the Big Three's wartime agreements and broken promises, and a continuity-and-change argument about America's role in the world can use the alliance as evidence of the shift from isolationism to global leadership. The move that earns points is not naming the three men. It's explaining what their cooperation produced (victory, the UN, occupation zones) and what their distrust produced (the Cold War).

## Big Three (leaders of the US, Soviet Union and Great Britain) vs The Big Four (Paris Peace Conference, 1919)

Different war, different leaders. The Big Four were the WWI victors at Versailles in 1919: Wilson (US), Lloyd George (Britain), Clemenceau (France), and Orlando (Italy). The Big Three were the WWII Allied leaders: FDR, Churchill, and Stalin. Quick check for the exam: if the Soviet Union is in the room, you're in WWII territory. If France and Italy are at the table and the topic is the Treaty of Versailles, it's WWI.

## Key Takeaways

- The Big Three were FDR (United States), Winston Churchill (Great Britain), and Joseph Stalin (Soviet Union), the leaders of the major Allied powers in World War II.
- Their cooperation is a textbook example of why the Allies won, which is exactly the cause the CED highlights under learning objective APUSH 7.13.A.
- The alliance was one of convenience, since two capitalist democracies and a communist dictatorship only worked together because defeating the Axis required it.
- At conferences like Tehran (1943) and Yalta (1945), the Big Three coordinated military strategy and planned the postwar world, including occupation zones in Germany and the United Nations.
- Stalin's broken Yalta promise of free elections in Eastern Europe is one of the clearest causes of the Cold War, making the Big Three the bridge between Unit 7 and Unit 8.
- By the Potsdam Conference in mid-1945, FDR had died and Truman had taken his place, and the cooperative spirit of the Big Three was already falling apart.

## FAQs

### Who were the Big Three in World War II?

President Franklin D. Roosevelt of the United States, Prime Minister Winston Churchill of Great Britain, and Premier Joseph Stalin of the Soviet Union. They led the major Allied powers and met at conferences like Tehran (1943) and Yalta (1945) to plan strategy and the postwar world.

### Were the Big Three actually allies who trusted each other?

Not really. They were allies of necessity united against Hitler, but deep ideological distrust between the capitalist US and Britain and the communist USSR never went away. That distrust resurfaced immediately after Germany's defeat and helped launch the Cold War.

### How is the Big Three different from the Big Four?

The Big Four were the WWI leaders at the 1919 Paris Peace Conference (Wilson, Lloyd George, Clemenceau, and Orlando), while the Big Three were the WWII Allied leaders (FDR, Churchill, and Stalin). If Stalin or the Soviet Union is involved, it's WWII.

### What did the Big Three decide at the Yalta Conference?

At Yalta in February 1945, they agreed to divide Germany into occupation zones, planned the United Nations, and got Stalin's promise of free elections in Eastern Europe. Stalin broke that promise, which became a major spark for the Cold War.

### Is the Big Three on the APUSH exam?

Yes, it falls under Topic 7.13 (World War II: Military) and learning objective APUSH 7.13.A, which credits Allied cooperation for victory over the Axis. It's most useful as essay evidence for why the Allies won and how wartime agreements led to the Cold War.

## Related Study Guides

- [7.13 World War II: Military](/apush/unit-7/world-war-ii-military/study-guide/3giKnoeivLFf1jQamalK)

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