General Hugh Mercer was the highest-ranking officer killed during the battle

Mawhood was reportedly bringing his troops back to Princeton when Mercer got the news. Washington gave Mercer instructions to withdraw his column to the right so he could attack the British before they could engage Washington's main army. When Mercer realized he wouldn't be able to stop Mawhood in time, he turned to join Sullivan instead of moving toward Mawhood's back. Mawhood sent a portion of the 55th Regiment to join the 40th Regiment in the town after learning that Mercer was in his rear and advancing to join Sullivan. Mawhood then deployed the remaining 55th, the 17th, fifty cavalry, and two artillery pieces to assault Mercer.

While he brought up the other detachments, Mawhood instructed his light forces to keep Mercer from moving. The British light infantry suddenly came while Mercer was strolling through William Clark's orchard. The volley from the British light infantry was high, which enabled Mercer time to turn his troops into the front lines of fight. The British light infantry were pushed back as Mercer's forces approached. At the top of the orchard, the Americans took up a position behind a fence. The British and outnumbered American infantry exchanged fire for nearly ten minutes after the American gunners commenced fire.

Because many of the Americans were using rifles, which couldn't be fitted with bayonets, they were overwhelmed when Mawhood ordered a bayonet charge. The British took both of the American cannons and turned them against the retreating soldiers. British soldiers approached Mercer and yelled at him, "Surrender, you damn renegade!" Mercer chose to resist rather than request a quarter. The British, thinking they had caught Washington, bayoneted Hugh Mercer and then left him for dead.