After conclusion of the Franco-American Alliance (6 February 1778) British forces in America had to give consideration to the new threat created by the powerful French fleet. General Clinton, who relieved Howe as British commander in America on 8 May 1778, decided to shift the main body of his troops from Philadelphia to a point nearer the coast where it would be easier to maintain close communications with the British Fleet. Consequently, he ordered evacuation of the 10,000-man garrison in Philadelphia on 18 June. As these troops set out through New Jersey toward New York, Washington broke camp at his winter headquarters in Valley Forge, and began pursuit of Clinton with an army of about 13,500 men. Advance elements under Mad. Gen. Charles Lee launched the initial attack on the British column as it marched out of Monmouth Courthouse (now Freehold), N. J., on 28 June, an extremely hot day. For reasons not entirely clear Lee did not follow up early advantages gained, and when British reinforcements arrived on the scene he ordered a retreat. This encouraged Clinton to attack with his main force. Washington relieved Lee and assumed personal direction of the battle, which continued until dark without either side retiring from the field. But, during the night, the British slipped away to Sandy Book, N. J., from where their fleet took them to New York City. The British reported losses of 65 killed, 155 wounded, and 64 missing; the Americans listed 69 killed, 161 wounded, and 130 missing. General Lee was subsequently court-martialed and suspended from service for disobedience and misbehavior. Washington's army moved northward, crossed the Hudson, and occupied positions at White Plains, N. Y.