Which organization was formed in 1955 for collective defense, including the USSR?

The Warsaw Pact, formed in 1955, was a collective defense treaty among the Soviet Union and seven other Eastern Bloc socialist republics in Central and Eastern Europe. Its creation was a direct response to NATO, which included Western countries and was seen as a military alliance threatening Soviet security interests. The Warsaw Pact established a unified military command and was a cornerstone of the Eastern Bloc's military strategy during the Cold War. It served to solidify the USSR's influence over its satellite states and provided a framework for mutual defense in the event of an attack. This organization lasted until the political changes in Eastern Europe in the late 1980s and early 1990s, which eventually led to its dissolution.

The other organizations mentioned do not have the same historical significance or context as the Warsaw Pact. The Czech Pact and Polish Pact are not widely recognized names associated with major military alliances from that era, while the term Soviet Pact is vague and does not designate a specific, recognized collective defense agreement comparable to the Warsaw Pact.