Question

east - west conflict in europe during the cold war
1945 - 1949 -- the soviet union forms the communist eastern bloc.
1947 -- the united states announces the truman plan.
1948 - 1949 -- the soviet union enforces the berlin blockade.
1949 - 1955 --?
1949 -- western powers form the north atlantic treaty organization.
1955 -- the soviet union creates the warsaw pact.

Explanation:

The missing event corresponds to the Western response to the 1948-1949 Berlin Blockade. Western powers launched a massive airlift to supply West Berlin with food, fuel, and other essential goods, bypassing the Soviet land blockade.

Answer:

The Western Powers conduct the Berlin Airlift to supply West Berlin.