Warren enlisted Paul Revere and William Dawes on April 18, 1775, to leave Boston and spread the alarm that the British garrison in Boston was setting out to raid the town of Concord and arrest rebel leaders John Hancock and Samuel Adams. Warren participated in the Battles of Lexington and Concord the following day, the opening engagements of the American Revolutionary War.

Warren had been commissioned a major general in the colony's militia shortly before the June 17, 1775 Battle of Bunker Hill. Rather than exercise his rank, Warren chose to participate in the battle as a privatesoldier, and was killed in combat when British troops stormed the redoubt atop Breed's Hill. His death, immortalized in John Trumbull's painting, The Death of General Warren at the Battle of Bunker's Hill, June 17, 1775, galvanized the rebel forces. Warren has been memorialized in the naming of many towns, counties, streets, and other locations in the United States, by statues, and in numerous other ways.