What key event occurred during the Berlin Blockade?

The key event during the Berlin Blockade was the supply of Berlin by air by Western powers. This operation, known as the Berlin Airlift, took place from June 1948 to May 1949 when the Soviet Union blocked all ground routes into West Berlin in an attempt to gain control over the entire city. In response, the United States and its allies organized an extensive airlift to deliver food, fuel, and other essential supplies to the citizens of West Berlin. Over the course of the airlift, planes made thousands of flights, successfully sustaining the population of West Berlin and demonstrating the commitment of the Western allies to support and protect the city.

The other options do not align with the timeline or events surrounding the Berlin Blockade. The construction of the Berlin Wall occurred later, in 1961, as a separate political action to stop the emigration from East to West Berlin. An attack by East Germany on West Berlin did not happen; rather, the blockade was a tense standoff between the East and West. Finally, the reunification of Germany did not occur until 1990, long after the Blockade had ended and was a result of different circumstances in the Cold War.