The Boston campaign was the opening campaign of the American Revolutionary War, taking place primarily in the Province of Massachusetts Bay. The campaign began with the Battles of Lexington and Concord on April 19, 1775, in which the local colonial militias interdicted a British government attempt to seize military stores and leaders in Concord, Massachusetts. The entire British expedition suffered significant casualties during a running battle back to Charlestown against an ever-growing number of militia.