The event that led directly to the formation of the Warsaw Pact was the creation of NATO in 1949.
Explanation:
The Treaty of Friendship, Collaboration and Mutual Assistance, better known as the Warsaw Pact for the city in which it was signed, was a military cooperation agreement signed on May 14, 1955 by the countries of the Eastern Bloc. Designed under the leadership of the Union of Soviet Socialist Republics (USSR), its express objective was to counteract the threat of the North Atlantic Treaty Organization (NATO), and in particular the rearmament of the German Federal Republic, to which the Agreements of Paris allowed to reorganize their armed forces.
