Leavitt was among those chosen to form Alpha Team - the first team of Sentinels - and participated in its first mission to journey to Fort Anchorage, Alaska to retrieve the Atomic Bomb from occupying Chimeran forces. The mission, however, became a disaster and saw the deaths of half of the team, and the loss of the bomb. Leavitt and the survivors of the mission - himself, Sergeants Benjamin Warner and Joseph Capelli - were retrieved by a submarine sent by SRPA to investigate the detonation of the bomb, which was done so by the team's leader, Lieutenant Murphy, to destroy a Chimeran battleship in the area, and by extension the ice-bridge the Chimera had formed from invading North America at the cost of Murphy's life.
SRPA Command ruled out the mission as a failure, but more than anything was a failure of leadership on the part of Murphy and Capelli, whom they basically botched the mission by putting their own safety ahead of the mission. Leavitt, however, impressed his superiors as, at a critical moment in the mission, he came up with the idea to ensure the bomb could be salvaged, though doing so would sacrifice themselves in the process.
Having proved himself for putting the sake of the mission first, Leavitt was promoted and made an officer; with the rank of Lieutenant, and, by August 1951, was in command of his own team, Echo Team. Leavitt would lead the team until his death in December 21, 1952 in which he was killed in Raleigh, North Carolina, after trying to destroy a Stalker production factory. Following his death, he was succeeded by Nathan Hale.