On 14 April, 1775, the military governor of Massachusetts, British Army General Thomas Gage received instructions to seize members of the Massachusetts’s Provincial Assembly, disarm minuteman militias, and arrest prominent Sons of Liberty leaders known to be hiding in the countryside outside of Boston. Gage had on several occasions already attempted to seize American militia stores and forcibly disband American militias, but this was the first time he had received specific instructions from London to do so. Originally written in January, the instructions authorized Gage to break up the illegal provincial assembly and arrest its members, even its loyalist members. However, every Massachusetts town had its own militia. Isolated, these were not too much of an issue since he assumed they would never fire on British regulars. Together though, they could form a rebel army that could possibly challenge his command in Boston. To form this army, the rebels would need vast stores of powder, supplies, and cannon. British spies reported that the rebels were amassing exactly that at Concord, about twenty miles west of Boston.
Concord was a crossroads town a day’s ride from the city that connected towns west, northwest, and southwest to Boston. It was a natural meeting place for the rebels to coordinate their activity and stores arms and equipment for future use. Due to the hostility of the American populace in the countryside, Gage didn’t want to have his men overnight outside of Boston. Seizing the stores at Concord was the first step in neutralizing the countryside long enough to seize the members of the provincial council. Concord was twenty miles away, a one day’s forced march and back for good troops, but only just. On the morning of the 15th, Gage relieved the light and grenadier companies of each of his regiments, the best troops he had, of all upcoming duties “til further orders”. This tipped off American spies who immediately sent word to rebel leaders of an impending British advance into the countryside. Concord was the obvious target.
On the night of 15 April, Paul Revere, a silversmith and engraver and a courier for the Son’s of Liberty Committee of Public Safety in Boston set off to warn the American rebels. He stopped first at Lexington where Samuel Adams and John Hancock were hiding in the parsonage to warn them of the impending British attempt to arrest them. Revere then proceeded to Concord where he warned its leaders that the British were coming to seize the rebel stockpile. Revere then turned around and headed home to Boston. On the way back, he stopped at Charlestown. There he coordinated with the local patriots a lantern signaling system in the Old North Church, whose belfry was the tallest in Boston. When the British operation began, one lantern would signal the British were marching across the Neck to Roxbury, two if they were moving by boat to Cambridge or Charlestown.
At Concord, Revere’s message set off a flurry of activity. Since the stores of weapons, equipment, cannon, and powder were scattered in fields, swamps, cellars, barns, attics, and yards of the town, moving the stores would take some time. On the 16th the residents of Concord began a frenzy of digging and uncovering, then dragging and moving the stores to towns further away from Boston.