The story of the opera is based on something that really happened in Russian history. The Russian people were ruled by a tsar (an emperor). The previous tsar Tsar Ivan IV was known as “Ivan the Terrible”. He was terribly cruel and the Russian people suffered badly under his rule. They were hungry, they were tortured and killed. When he died his son became Tsar, but he was mentally retarded, so a group of powerful people including Boris Godunov had to rule for him. Ivan also had another son, but he disappeared. He was almost certainly murdered, and Boris Godunov, who wanted to become tsar himself, had probably ordered him to be murdered (for the sake of the opera, Mussorgsky assumes that he was indeed guilty of his murder). Then he persuaded the Russian people that they should choose him to be their tsar.