The Leviathan was an Alliance battle cruiser under the command of Kostya Tulev, and was flagship of the Second Battlecruiser division. During the fight back to Alliance space, Tulev's calm demeanor and patience was an asset to Geary, who normally assigned the Second Battlecruiser division to defend the four fleet auxiliary ships. Leviathan survived the war, and later served with the Alliance First Fleet in its expedition into unexplored extraterrestrial space. Leviathan and the rest of the Alliance First Fleet encountered the Defender Fleet as they returned from the far reaches of Syndic space, and chased it back to it's base of operations inside a binary star system. It was here that Leviathan was finally destroyed, as it collided with a Defender Fleet warship, leaving no survivors.