This map is part of a series of 16 animated maps showing the history of Europe and nations since 1945.
Given the threat of a Soviet military presence, Western Europe and the United States decided to create a military alliance. After negotiations, they met in April 1949 to sign the Atlantic Pact as a first step towards the creation of the North Atlantic Treaty Organization (NATO).
This Pact brought together the United States and Canada in North America and 10 European countries: France, the United Kingdom, Belgium, the Netherlands, Luxembourg, Italy, Norway, Denmark, Iceland and Portugal.
From its inception, NATO was expected to be a flexible military alliance: its members agreed to provide mutual assistance in the event of an attack against any other member in Europe or in North America. But with growing international tension after the Korean War (1950-1953), NATO members decided to build up integrated military structures; these were initially located in France, but were later transferred to Belgium.
In 1952, NATO enlarged its membership to include Greece and Turkey and again in 1955 to admit the Federal Republic of Germany. Spain became a member in 1982.
As the Atlantic Alliance came into existence, the Soviet Bloc decided to make similar moves. First, the USSR signed treaties for bilateral military assistance with the socialist republics. Immediately after the Federal Republic of Germany became a member of NATO, the USSR and Eastern European countries established the Warsaw Pact in May 1955. Placed under Soviet command, this Alliance pooled together the armies of the seven Eastern European countries: Poland, Czechoslovakia, Hungary, German Democratic Republic (GDR), Romania, Bulgaria and Albania.
The Warsaw Pact was dissolved in 1991.