In 1949, the Americans, British, and French combined their zones of occupation in West Germany to establish the Bundesrepublik Deutschland (Federal Republic of Germany).

The Soviets responded by forming the Deutsche Demokratische Republik (German Democratic Republic) in East Germany. 

Encyclopedia Britannica

In May 1955, ten years after the defeat of Nazi Germany in WWII, West Germany joined the North Atlantic Treaty Organization (NATO) in a move to counter potential Soviet expansion in western Europe.

With entrance into NATO, the Federal Republic of Germany became integral to the defense of Western Europe.