The battle started when Joseph Hooker hit Lee's left flank. This battle is the single bloodiest day in American military history. The north had many more soilders (numbers above), but the southern fighting ability kept the battle even. Every Union charge was met by a powerful Confederate counter-attack, with neither side able to get too much over the other. A.P. Hill sealed the battle by bringing his forces in to support Lee's forces. With the added support and McClellan's non-aggressive tactic the battle wasn't a definitive victory for either side and ends as a draw.