Trenton was a great victory but it did not cause any loss against the British regular army, only mercenaries. Washington decided to strike what he believed was an isolated part of Charles Cornwallis’ army near Princeton to build on the momentum of Trenton. Cornwallis was trying to attack Washington with about 9,000 men and he left 1,200 in Princeton under the command of Charles Mawhood.
Cornwallis found Washington at Trenton but arrived too late in the day to make an attack. Washington decided to move on to attack Princeton instead and by 2 AM the army was in motion leaving Trenton. The ground was frozen which made it easier to move the heavy artillery. Washington had hoped to be in Princeton before dawn but was running behind schedule. He decided to take a shortcut along a road that went through the farm of Thomas Clark.
Mawhood was actually already in motion. Cornwallis had ordered him to Trenton during the night. When his men left town they sighted Washington’s army and he turned his force around and headed back toward Princeton.
Hugh Mercer’s Colonial troops had been ordered to burn a bridge at Stony Brook and were now in Mawhood’s rear. Mercer wanted to rejoin Washington but Mawhood thought this was a tempting target and moved to attack Mercer. After about 10 minutes of firing Mawhood ordered a bayonet charge and Mercer’s force ran. Mercer himself was surrounded but when called on to surrender chose to resist. He was bayoneted by British soldiers who thought he was Washington.
Fresh militia under John Cadwalader arrived but they had little instruction in battlefield movements and no combat experience. They broke when they saw Mercer’s men running. Colonial artillery arrived and managed to hold Mawhood’s men back for several minutes. During this time Washington himself attempted to rally the broken ranks as the Virginia Continentals and Pennsylvania Rifleman followed by New Englanders began to arrive. Washington himself led his men into the field and when both sides were about 30 yards apart they fired.
Superior Colonial numbers began to tell as the New Englanders were able to flank the British and the riflemen picked off soldiers. Mawhood ordered a retreat but found Colonials blocking his way. He broke through with a final bayonet charge. Some British soldiers sought refuge in Nassau Hall in Princeton and were compelled to surrender when Alexander Hamilton brought up 3 cannon and began blasting away at the building.
Washington wanted to push on to New Brunswick but was talked out of it by his senior generals and instead he moved his army to Morristown where it took up winter quarters. Cornwallis abandoned Trenton and moved to New Brunswick. Casualty figures for the battle vary. The British lost between 250 and 450 men and the Colonials lost 60 and 80. While a minor victory it was a victory and Colonial morale and confidence grew. Today part of the battlefield is preserved as part of the Princeton Battlefield State Park.