After Lenin's death Stalin joined in a troika with Grigory Zinovyev and Kamenev to lead the country. With these temporary allies, Stalin acted against his arch rival Trotsky, the foremost candidate for Lenin's mantle. Once the threat of Trotsky was eliminated, however, Stalin reversed course, aligning himself with Nikolay Bukharin and Aleksey Rykov against his former partners. Trotsky, Zinovyev, and Kamenev in turn challenged Stalin as the "left opposition." By skillful manipulation and clever sloganeering, but especially by interpreting Lenin's precepts to a new generation coming of age in the 1920s, Stalin bested all his rivals.
By his 50th birthday (1929), Stalin had cemented his position as Lenin's recognized successor and entrenched his power as sole leader of the Soviet Union.
Stalin reacted to lagging agricultural production in the late '20s by a ruthless, personally supervised expropriation of grain from peasants in Siberia. When other crises threatened in late 1929, he expanded what had been a moderate collectivization program into a nationwide
offensive against the peasantry. Millions were displaced, and unknown thousands died in the massive collectivization. The industrialization campaigns over which Stalin presided in the 1930s were much more successful; these raised the backward USSR to the rank of the industrial powers.
In the mid-1930s Stalin launched a major campaign of political terror. The purges, arrests, and deportations to labor camps touched virtually every family. Former rivals Zinovyev, Kamenev, and Bukharin admitted to crimes against the state in show trials and were sentenced to death. Untold numbers of party, industry, and military leaders disappeared during the "Great Terror," making way for a rising generation that included such leaders as Nikita Khrushchev and Leonid Brezhnev. Fear instilled by a political secret police formed an essential part of the
system called Stalinism.
In part because the purges stripped the military of its leadership, the Soviet Union suffered greatly in World War II. Stalin personally directed the war against Nazi Germany. By rallying the people, and by his willingness to make great human sacrifices, he turned the tide against the Germans, notably at the Battle of Stalingrad. Stalin participated in the Allies' meetings at Tehran (1943), Yalta (1945), and Potsdam (1945), where he obtained recognition of a Soviet sphere of influence in
Eastern Europe, and after the war he extended
Communist domination over most of the countries liberated by the Soviet armies. His single-minded
determination to prevent yet another devastating assault on the USSR from the West had much to do with the growth of the cold war. In his last years, increasingly paranoid and physically weak, Stalin apparently was
about to start another purge. In January 1953 he
ordered the arrest of many Moscow doctors, mostly Jews, charging them with medical assassinations. The so-called Doctors' Plot seemed to herald a return to the 1930s, but Stalin's sudden death on March 5, 1953, in Moscow
forestalled another bloodbath.

Stalin visits Lenin at his home in 1922

Young Stalin in Gori Georgia church school

Stalin
Negotiating with the Germans

End of Stalin's Biography