The American Revolutionary War began near Boston, Massachusetts with the Battles of Lexington and Concord, in which a group of local militias constituted the American side (the "Patriots"). On April 19, 1775, a British force 800 strong marched out of Boston to Concord intending to destroy patriot arms and ammunition. At 5:00 in the morning at Lexington, they met about 70 armed militiamen whom they ordered to disperse, but the militiamen refused. Firing ensued; it is not clear which side opened fire. This became known as "the shot heard round the world". Eight militiamen were killed and ten wounded, whereupon the remainder took flight. The British continued on to Concord and were unable to find most of the arms and ammunition of the patriots. As the British marched back toward Boston, patriot militiamen assembled along the route, taking cover behind stone walls, and sniped at the British. At Meriam's Corner in Concord, the British columns had to close in to cross a narrow bridge, exposing themselves to concentrated, deadly fire. The British retreat became a rout. It was only with the help of an additional detachment of 900 troops that the British force managed to return to Boston. This marked the beginning of the war. It was "three days after the affair of Lexington and Concord that any movement was made towards embodying a regular army".