Michael's mother, Dowager Empress Marie, moved back to Anichkov Palace with Michael and Olga. Like most male members of his family, Michael was enrolled in the military. He completed training at a gunnery school and joined the Horse Guards Artillery. In November 1898, he attained legal adulthood and, just eight months later, became heir presumptive to Nicholas as the middle brother, George, was killed in a motorcycle accident. George's death and the subsequent change in the line of succession highlighted that Nicholas lacked a son. As the succession was limited to males, his three daughters were ineligible. When Nicholas's wife, Alexandra, became pregnant in 1900 she hoped that the child would be male. She manoeuvred to get herself declared regent for her unborn child in the event of Nicholas's death, but the government disagreed and determined that Michael would succeed regardless of the unborn child's gender. She was delivered of a fourth daughter the following year.