The battle of Monmouth Courthouse was not only the last major action in the Northern theater, it was also the longest and hardest-fought engagement of the entire Revolutionary War (1775-1783). When the British abandoned Philadelphia to return to New York City, American troops harassed their retreat. On the morning of 28 June 1778, General Lee, George Washington's lieutenant, attacked the British rearguard but his attack went badly wrong. The British rearguard, now reinforced, threw Lee's troops into a headlong retreat. Lee was relieved of his command and Washington's Continentals then stood toe-to-toe with the British, bloodily repulsing a series of powerful attacks by crack troops.