| Ivan VI was the great-grandson of Tsar Ivan V, and the first boy to be born among those descendants. He was named the heir of reigning Tsaritsa Anna (Ivanovna), his great-aunt, almost as soon as he was born. Anna died and Ivan became tsar in 1730 at the age of two months. At first, the late Empress's Anna's favorite Ernst-Johann Biron was his regent, but after a few weeks a palace revolt put Ivan's mother Anna Leopoldovna in his place (and sent Biron to Siberia). But if Biron the German had been unpopular, the German father and half-German mother of Ivan were even more disliked by the Russian people.
Elizabeth, daughter of Peter the Great and his second wife Catherine I, gradually gathered support from the army, the nobles, and even Sweden, which declared war on Russia in early 1741, claiming as some of its reasons the fact that Peter the Great's living descendants had been kept off the throne. Anna Leopoldovna actually got word of the plotting against her, but Elizabeth convincingly denied everything and was not imprisoned. The day after Elizabeth's denial, 24 November 1741, she led the guards against Anna and Ivan and won.
Elizabeth did not believe in executions, so Ivan was imprisoned at the age of 15 months and stayed in prison throughout the twenty-one years of her reign. There had been conspiracies in his name, but Elizabeth squashed them all before they could involve him. Supposedly he was hardly taught anything about the outside world except Orthodox Christianity, but somehow got the information that he was a prince, even though he was merely "Prisoner Number One" to the guards around him. The two guards closest to him were really just as much prisoners, as they could not leave the fortress or even be transferred elsewhere in it; they apparently tended to mock and taunt him even when the governor of the fortress warned them against it.
Shortly after the accession of Catherine the Great in 1762, she came to visit him. She later claimed he had been weak-minded, but she would probably say that to bolster her own presence as Tsaritsa. Shortly after the meeting she issued orders that if anyone came to try and break him out, that Ivan be killed rather than allowed to escape. Less than a year later, a Ukrainian named Mirovich, who worked in the fortress where Ivan was held, found out who he was and resolved to free him and put him back as Tsar. He persuaded the soldiers he commanded to follow him, and they managed to storm into his cell, but Ivan was then already dead from the swords of his guards. He was 24.
Sources: Gina Kaus' Catherine: the Portrait of an Empress, Donald Raleigh and A.A. Ishkanderov's The Emperors and Empresses of Russia: Rediscovering the Romanovs, as well as those listed under Monarchs of Russia. | 
