Joseph Stalin's faith was Christian growing up, but as an adult, he began to take on Marxism and communism as his main belief systems. At one point, Stalin claimed to be an atheist and studied the works of Charles Darwin. Other authors that shaped his belief system were Engels and Lenin.
Stalin was born with the name Iosif Vissarionovich Dxhugashvili in 1879. He studied at a seminary for five years as a young adult and began reading books on Marxism and Darwin during that time.
He eventually became the leader of the Communist Party and forced collectivism on the people of the Soviet Union. During his reign, the collection of crops cost millions of lives. Stalin believed in purging the population of those who he didn't feel were fit to live, according to his interpretation of the teachings of Marxism. If someone had a physical or mental challenge of some sort, he believed that it was the duty of the collective to kill them. Thousands of people whom he considered "enemies of the state," or those with challenges, were executed. Millions of others were sent to slave camps.
Part of Stalin's purging took place in the Red Army, and as a result, Stalin was not prepared to fight Hitler. However, he succeeded in these battles.