After the regulars had moved through the successive ambushes and attacks at Merriam's Corner, Hardy's Hill and the Bloody Angle on their march eastward toward Boston through Concord and Lincoln, they came to boulder-strewn pastures owned by Tabitha Nelson. To the east of these fields, there was a rocky hill covered with dense brush and trees near the Lexington-Lincoln line. Captain John Parker and his Lexington militia were there, waiting for the regulars to return. The Lexington men had lost a quarter of their number when the regulars fired on them on the Lexington Green earlier that morning. This time, Parker and his men knew what they had come to do, and waited for the regulars with determination.

Parker waited until the regulars were directly in front his men, then opened fire with a volley that wounded Colonel Smith in the thigh and knocked him from his saddle. The front of the column stopped briefly under the fire, which was the worst possible reaction. As the rear of the column packed into its front, Major Pitcairn galloped up to get the regulars moving again. With Smith wounded, Pitcairn assumed active command of the column and sent troops up the hill to drive the Lexington militia away. The regulars succeeded, but this took time and allowed other militia and minute companies to get ahead of the column again and continue the ring of fire. The provincials were able to ambush the regulars again just a few hundred yards down the road. Pitcairn again ordered his men up the hill to drive the provincials away. They succeeded again, although Pitcairn's marines paid a heavy price for holding off the converging provincials.

No sooner had the column of regulars once again begun to move forward than it ran into another group of provincials at Fiske's Hill. Pitcairn was thrown from his horse here and injured in the fall, and more regulars were killed or wounded. At this point, the column effectively disintegrated as a military force. According to Ensign DeBerniere, one of their officers, "when we arrived within a mile of Lexington, our ammunition began to fail, and the light companies were so fatigued with flanking they were scarce able to act, and a great number of wounded scarce able to get forward... we began to run rather than retreat in order-the whole behaved with amazing bravery but little order; we attempted to stop the men and form them two deep, but to no purpose..." Finally, the officers "got to the front and presented their bayonets, and told the men if they advanced they should die: upon this they began to form under a very heavy fire."

Clearly, the provincial militia was about to destroy the column as a fighting unit. At that moment, however, a cheer rose from the front of the column. When the officers holding back their men at bayonet-point turned around, they saw the reason for the cheering. Across Lexington they could see a brigade of regulars marching into Lexington under the command of Brigadier the Right Honorable Hugh Earl Percy. Percy later wrote to his father that "I had the happiness of saving them from inevitable destruction."

Percy's  and what is left of Pitcairn's Outfit continue on to Boston (Menotomy, ambush)