Following the end of World War II, the Soviet Union emerged as one of the two great powers, the other being the United States. Allied during the war because of their common disgust with the regimes of the German and Japanese states, the two powers turned on each other following the war's end. Part of this was ideological; communism was, by definition, the enemy of capitalism, and so the two sides were clearly separated on those grounds. There was also the issue of Europe: who would have control, what control would they have, and how would it be managed? Germany, Britain, and much of Eastern Europe was devestated by the war, and their losses, while not as bad as those in the Soviet Union, were nonetheless severe.
The USSR came to dominate Eastern Europe, other than Greece, and to control much of the Balkans region as well. In addition, the Soviets continued to improve their economic and industrial production, although this was frequently to the detriment of the general population. The Fourth of the Five Year plans was introduced in 1946, and it stressed, as the early plans had, heavy industry. Economically, the Soviet Union benefitted from the reparation payments that were forced on the Germans and their allies; some of the reparations included the dismantling and moving of factories from German held areas to the Soviet Union. Agriculture was also stressed, but at a slightly lower level than heavy industry.
Politically, the Soviet Union remained stable; Stalin was more firmly in power than ever (as the great patriotic leader), and a cadre of his supporters had emerged as potential successors, including George Malenkov, Lavrentii Beria, and Nikita Khrushchev. Malenkov was, at least for a time, Stalin's chosen successor, but such a position was not likely to be a stable one.

Stalin's Last Years

The war had done nothing to mellow Stalin. While the Allies and the Soviets worked together through 1945 and into 1946, it was clear that a break was coming at some point. The two sides could not reach agreement about the issue of atomic power, and when the United Nations formed the Atomic Energy Commission, the Soviets refused to participate. The Soviet Union also refused to withdraw its troops from the countries it had occupied during the war, which the rest of the Allies had done or were in the process of doing. The decision by the Soviets to seize control of the countries of Eastern Europe was the final straw. The USSR installed governments in Albania, Bulgaria, Romania, Hungary, Poland, Yugoslavia, and East Germany. In some of these countries, such as Albania, the communist movement had been very strong before the war and had helped to thwart the Axis powers; as a result, the communist party was welcomed. In other countries, however, communism had been largely non-existant, and the take over by the USSR was therefore a shock. Only two countries were not seized: Greece, because of the efforts of the Allies to prevent a communist take over, and Finland.
Efforts by the Allied powers to help economically were rebuffed. The Marshall Plan, introduced in the summer of 1947, provided economic aid to countries in Europe, but the Soviets refused to accept the help fearing that it would make them appear beholden to the West. In 1949, twelve of the western countries, including the United States, formed the North Atlantic Treaty Organization. The USSR suffered several blows during this time, including the loss of Yugoslavia from its bloc when the leader of the Yugoslav communists, Marshall Tito, refused to accept Soviet control over the country's economic plans. The West and the Soviets also came to conflict in the United Nations, where the Soviets used their veto power in the Security Council to thwart the plans of the West. In China, the Chinese Communists defeated the Nationalists in 1949, securing control of that country; the West had largely abandoned the nationalists by that time, fearing the investment would be too costly. When communism spread into Korea, the West chose to act, resulting in actual hostilities between American and Soviet troops fighting on the sides of the South and North Koreans, respectively. Most of the fighting had ended by the summer of 1951, although it would take Stalin's death to finally conclude a peace treaty.
Stalin's death was a watershed in the history of the Soviet Union. The Great Patriotic Leader had been in increasingly bad health through 1952, and in early 1953 it was announced that a plan had been uncovered that pointed to a conspiracy of doctors who had been responsible for poisoning many of the leaders of the Communist Party. These men were rounded up and were almost certainly headed for death when Stalin suffered a fatal stroke and died on March 5, 1953. The doctors of the so-called "Doctors' Plot" were freed, and the Soviet Union began life under a new regime, headed up initially by a triumvirate: Malenkov, Stalin, and Khrushchev.

Khrushchev's Rise and Fall

Nikita Khrushchev's rise to power was, in a word, amazing. The son of a Ukrainian miner, Khrushchev rose through the Ukrainian communist party and eventually became one of Stalin's most trusted advisors, possibly because, like Stalin himself, he was not a particularly good theorist. In the summer of 1953, an apparent coup led to the execution of Beria, and by early 1955 Malenkov had retired, leaving Khrushchev in power alone. One of his first actions, in early 1956, was the so called "Secret Speech" to the Twentieth Party Congress, in which Khrushchev denounced many of Stalin's actions, refering to the "cult of personality" that Stalin had cultivated. Part of this was to deflect criticism from those members of the party who had been privy to some of the worst abuses but had kept silent; as Khrushchev later stated, everyone was so terrified of Stalin that no one dared to cross him. The first years of Khrushchev regime were referred to as the thaw, as he attempted to end certain parts of the Cold War, especially those within the Soviet Union itself. Censorship laws were lightened; the powers of the secret police (which had been dominant under the control of Beria) were lessened; members of Stalin's entourage who had been guilty of egregious crimes (such as Beria) were removed. However, within five years, it became clear that Khrushchev's powers were declining; he had managed to have Stalin's body removed from Lenin's tomb, where it had been placed shortly after Stalin's death, and buried at the Kremlin instead. In 1960, relations with China had deteriorated to such a state that by 1963 the situation appeared irreparable. In 1962, Khrushchev was humiliated when he was forced to back down over the issue of missiles that had been placed in Cuba; this confrontation, which was probably the closest that that Cold War ever got to becoming an actual "Hot" war (that is, one in which the combatants actually go into battle directly against each other), is more commonly known as the Cuban Missile Crisis, and it for all intents and purposes marked the end of Khrushchev's career. However, the means by which Khrushchev was deposed marked a new era in the regime of the Communists; he was simply forced into retirement rather than executed. Instead, he spent the rest of his life on his dacha writing his memoirs.