(North Atlantic Treaty Organisation)
NATO is a military alliance established on 4 April, 1949. It sought to create a counterweight to Soviet armies stationed in central and eastern Europe after World War II. Its founding members were Belgium, Canada, Denmark, France, Iceland, Italy, Luxembourg, The Netherlands, Norway, Portugal, Turkey, the United Kingdom, and the United States. Joining the original signatories were Greece and Turkey (February 1952), West Germany (May 1955), Spain (May 1982), East Germany by virtue of integration into reunified Germany (October 1990) , the Czech Republic, Hungary, and Poland (March 1999) and Bulgaria, Estonia, Latvia, Lithuania, Romania, Slovakia and Slovenia (March 2004). France withdrew from the integrated military command of NATO in 1966, but it remains a member of the organisation.

(The Warsaw Treaty Organisation)
WTO was, as the name implies, signed in the capital of Poland, on 14 May 1955 between representatives of the socialist republics of Albania, Bulgaria, Czechoslovakia, Hungary, Poland and the USSR. East Germany joined in 1956. Of the East European People's Democracies, Yugoslavia was the sole non-signatory state, but it was soon joined by Albania, which formally withdrew from its obligations in 1968. Romania, on the other hand, never officially denounced the Treaty, but increasingly distanced itself from it from the early 1960's. After the end of the Cold War, the Warsaw Treaty Organisation was formally dissolved on 1 July 1991.