On April 14 HMS Nautilus arrived in Boston with a letter for Gen. Thomas Gage, governor of Massachusetts and commander in chief of the British army in North America. It had been written in late January by Britain’s colonial secretary, Lord William Dartmouth, to express concerns that the rebel element in Massachusetts was getting out of control. Since taking office in May 1774, Gage had been wary of cracking down too hard on dissent, fearing that his force would be inadequate should the colony rise in open rebellion. But Dartmouth had seen enough of Gage’s timidity; the time had come to act.

In fact, Gage had already taken steps to suppress the rebels. In September his troops had seized a large amount of powder from a storehouse in Charlestown, and as recently as April 8 a raid on Fort Pownall, at the mouth of the Penobscot River in Maine (then a part of Massachusetts), had taken sixteen cannon, nearly five hundred cannonballs, and much other valuable matériel out of rebel hands. Gage had also concentrated more than three thousand troops in Boston, sent men and arms to protect Tories elsewhere in the province, arranged to mobilize Canadians and Indians, mapped areas of likely conflict, built a network of spies, and thoroughly marched and drilled his men.

These defensive measures were not enough for Dartmouth, who directed Gage “to arrest and imprison the principal actors & abettors in the Provincial Congress (whose proceedings appear in every light to be acts of treason & rebellion).” Unfortunately, the provincial congress adjourned the day after the letter arrived.

Anticipating this possibility, Dartmouth told Gage that “there are other Cases that must occur, in which affording the Assistance of the Military will probably become unavoidable.” Such a confrontation “would become a Test of the People’s resolution to resist”—a test, he was confident, that the ill-trained and undisciplined colonists were bound to fail. Being closer to the scene, Gage was less confident about the redcoats’ supremacy in the field. Yet virtually every line of Dartmouth’s letter bespoke mounting impatience with Gage’s cautious policies.

Gage lost no time putting Dartmouth’s orders into effect. On April 18 he sent the following orders to Lt. Col. Francis Smith of the 10th Regiment: “A Quantity of Ammunition and Provision together [with] numbers of Cannon and small Arms having been collected at Concord for the avowed purpose of supporting a Rebellion against His Majtys Government, you will march with the Corps of Grenadiers and Light Infantry put under your Command with the utmost Expedition and Secrecy to Concord; where you will seize and destroy all the Artillery and Ammunition Provisions Tents & all other Military Stores you can find. . . .” Smith’s troops—seven to eight hundred strong, with an additional fourteen hundred to join them later on—left Boston that night for what promised to be an uneventful thirty-mile march through Lexington to the