High Quality Content by WIKIPEDIA articles! The Boston campaign was the opening campaign of the American Revolutionary War. The campaign was primarily concerned with the formation of American colonial irregular militia units, and their transformation into a unified Continental Army. The campaign`s military conflicts started with the Battles of Lexington and Concord on April 19, 1775, in which colonial militias mustered to defend against the seizure of military stores in Concord, Massachusetts by British Army regulars. Some British units were defeated in a confrontation at Concord`s North Bridge, and the entire British expedition suffered significant casualties during a running battle back to Charlestown against an ever-growing number of colonial militia.