Final answer:
Cominform was established on September 22, 1947, to guide European communist parties post-WWII with the Soviet Union taking a leading role. Yugoslavia was expelled from Cominform in 1948, leading to it seeking assistance from the U.S. and later trading with both Western and Eastern Blocs.
Step-by-step explanation:
Cominform was established on September 22, 1947. It was created as the Information Bureau of the Communist and Workers' Parties and its main purpose was to ensure cooperation among European communist parties and give direction in the struggle against anti-communist influences, particularly in Western Europe after World War II. The Soviet Union played a leading role within Cominform, providing guidance to other member states.
In 1948, just a year after its formation, Cominform expelled Yugoslavia due to conflicts with the Yugoslavian leader, Josip Broz Tito, who later turned to the United States for help. This allowed Yugoslavia to avoid economic isolation, as its relations with other Eastern Bloc countries were severely affected by the expulsion.
Cominform's existence was indicative of the growing tensions during the early Cold War period, providing a platform for the Soviet Union to extend its influence over other communist nations and for collective security among those states against perceived Western aggression.