What is NATO? - Definition & Country Members

Instructor: Christina Boggs

Chrissy has taught secondary English and history and writes online curriculum. She has an M.S.Ed. in Social Studies Education.

After World War II, the United States and its Western European allies saw the need to defend one another. This lesson discusses the origins, purpose, and members of the North Atlantic Treaty Organization (NATO).

After World War II

When World War II came to an end in 1945, there were two major world powers left standing: the United States and the Soviet Union. As you may know, these two countries had very different visions for the post-war world. President Harry S. Truman envisioned a democratic Europe that participated in the free-market. Soviet Premier Joseph Stalin, however, planned to spread communism.

In the years following the war, Harry Truman and his advisers realized that Europe was in desperate need of aid. The United States' allies were struggling to rebuild. The countries of Western Europe were in ruins, and so were their defenses. From 1947 to 1948, a series of events only heightened these facts. Civil war in Greece and conflict in Turkey led President Truman to commit financial and military aid to both countries. In 1948, the Soviet Union backed a coup d'état in Czechoslovakia and started the Berlin Blockade that cut off the other allies from Germany's capital. In the eyes of the United States and its allies, something had to be done.

Ruins in Caen, Normandy, after bombings in July of 1944
caen in ruins

Founding NATO

In 1948, Great Britain, France, Belgium, the Netherlands, and Luxembourg signed the Brussels Treaty, a collective security agreement that committed the five countries to defend each other in the event of an attack. Meanwhile, across the pond, the United States was contemplating the need for a similar agreement between itself and Western Europe. In 1949, twelve countries entered into the North Atlantic Treaty Organization (NATO):

  • United States
  • Canada
  • Great Britain
  • France
  • Belgium
  • The Netherlands
  • Luxembourg
  • Iceland
  • Italy
  • Denmark
  • Norway
  • Portugal

Signing of the North Atlantic Treaty Organization
Signing of the North Atlantic Treaty Organization

Each of these countries agreed to a mutual defense pact; if any of the NATO member countries was attacked in Europe or North America, the other members promised to come to their defense.

NATO gained two more members in 1952 when Greece and Turkey joined the organization. The Federated Republic of Germany (also known at the time as West Germany) joined NATO in 1955.

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