Berlin Blockade
The Soviet Union began the blockade because they thought the western half of Germany (controlled by the UK, USA and France) was becoming too strong, because one currency had recently been introduced throughout the entire western half - the Deutsche Mark. The Soviets were worried that a single currency would help the economy of the western half recovered quickly from the damage caused by the Second World War, and that this stronger western half would eventually develop into a country (it eventually did, called West Germany). The Russians wanted one Germany, without an army, that they could easily control. The Nazi invasion of the Soviet Union had killed one in seven Soviet people, and the Soviets feared that Britain, France and America might try to launch their own invasion at some point in the future. They therefore wanted as much land between them and France as possible, so that any major war would be fought in central Europe, and not in the Soviet Union where Soviet civilians might be killed (which is what had happened during WWII).