Over the next decade, Stalin worked with the political underground in the Caucasas. During this time, between 1902 and 1917, he was repeatedly arrested and exiled to Siberia. He was an adherent of Vladimir Lenin's doctrine of a strong centralist party of professioanl revolutionaries, which was called Bolsheviks. There is also some evidence that Stalin, who had taken the pseudonym of Koba, was in the employ of the Tsar's Secret police. According to Olga Shatunovskaya, a member of the party since 1916, and at one time the secreatry to Stephan Shaumyan, chairman of the Baku Commune, he was.

             His work gained him a place on the movement's Central Committee in 1912, and in 1913 he adopted the name Stalin, which means "man of steel" in Russian. It was during this time that Stalin was maried briefly to Ekaterina Svanidze in 1907. She died after three years, but they had one son together, whose name was Yakov Dzhugashvili. At the funeral he is said to have made a statement about any warm feelings he had for people, having died with his wife. His son, with whom he did not get along, served in the Red Army during the Second World War, where he was captured by the Nazis. Although the Nazis offered to exchange him for a German officer of higher rank, Stalin refused and his son was later killed trying to excape.

             In 1917 Stalin was editor of Pravda while Lenin was in exile. After the February revolution, the first stage in the Russian Revolution, Stalin was elected to the Politburo in May, a position he held for the rest of his life. Stalin played only a minor role in the October revolution, apparently not distinquishing himself. Later, he embellished his actions after he came to power.

             In 1919 a Politburo was created initially with five members, to run the Communist Party of the Soviet Union (CPSU) on a day to day basis. Previously, the highest body of the Party had been the Central Committee.