The country was thoroughly alarmed. The yeomanry were hurrying from every quarter to the scene of action. As the British began their retreat, the Americans began the work of sore and galling retaliation. Along the open road, the former were harassed incessantly by rustic marksmen, who took deliberate aim from behind trees, or over stone fences. Where the road passed through woods, the British found themselves between two fires, dealt by unseen foes, the minute men having posted themselves on each side among the bushes. It was in vain they threw out flankers, and endeavored to dislodge their assailants; each pause gave time for other pursuers to come within reach, and open attacks from different quarters. For several miles they urged their way along woody defiles, or roads skirted with fences and stone walls, the retreat growing more and more disastrous; some were shot down, some gave out through mere exhaustion; the rest hurried on, without stopping to aid the fatigued, or wounded. Before reaching Lexington, Colonel Smith received a severe wound in the leg, and the situation of the retreating troops was becoming extremely critical, when, about two o'clock, they were met by Lord Percy, with a brigade of one thousand men, and two field-pieces. His lordship had been detached from Boston about nine o'clock by General Gage, in compliance with Colonel Smith's urgent call for a reinforcement, and had marched gaily through Roxbury to the tune of "Yankee Doodle," in derision of the "rebels." He now found the latter a more formidable foe than he had anticipated. Opening his brigade to the right and left, he received the retreating troops into a hollow square; where, fainting and exhausted, they threw themselves on the ground to rest. His lordship showed no disposition to advance upon their assailants, but contented himself with keeping them at bay with his field-pieces, which opened a vigorous fire from an eminence. Hitherto the Provincials, being hasty levies, without a leader, had acted from individual impulse, without much concert; but now General Heath was upon the ground. He was one of those authorized to take command when the minute men should be called out. That class of combatants promptly obeyed his orders, and he was efficacious in rallying them, and bringing them into military order, when checked and scattered by the fire of the field-pieces. Dr. Warren, also, arrived on horseback, having spurred from Boston on receiving news of the skirmishing. In the subsequent part of the day, he was one of the most active and efficient men in the field. His presence, like that of General Heath, regulated the infuriated ardor of the militia, and brought it into system.