Lee, as Washington's senior subordinate, was initially appointed commander of the advance force, but turned it down because of his doubts about the plan. However, when the force was increased to 5,000 men and the command offered to the Marquis de Lafayette, Lee changed his mind and insisted on the command.
Lee met with his subordinates but failed to give them proper orders, resulting in a piecemeal and disorganized attack on June 28 against the British rear guard under Lieutenant General Charles Cornwallis. After several hours of fighting in the hot weather, the British counterattacked and Lee ordered a retreat, which rapidly became a rout.
Washington, advancing with the main force along the Monmouth road, encountered Lee and his fleeing troops, with the British in pursuit. After a heated discussion with Lee, Washington relieved him of command and sent him to the rear. He then rallied Lee's troops, who delayed the British pursuit until the main force could take up positions further to the west.
The remnants of Lee's forces then withdrew to the main American force, where the newly-trained Continental Army troops held the British, repelling several attacks. The British fell back, rested, and resumed their march to the northeast during the night. The exhausted Americans could not pursue.
The next morning the Americans found the British had slipped away during the night, continuing their march without incident to Sandy Hook, arriving there on June 30. The British force was then transported by the Royal Navy across Lower New York Bay to the safety of Manhattan.
The battle was a tactical British victory, as the rearguard successfully covered the British withdrawal. However, strategically it was an American victory, as they were left in possession of the field, and had demonstrated that the Continental Army regiments could stand against the British regulars.