The Battles of Lexington and Concord were essentially a running battle through the countryside outside of Boston. This conflict marked the beginning of the Revolutionary War. The battle began when General Thomas Gage, commander of British troops in Boston, sent a detachment of men to Concord with the aim of seizing weapons, ammunition, and powder stashed there. They also hoped to arrest some leaders of the insurgency in Massachusetts along the way. People throughout the region were alerted to the march by a network of informants and alarms, and by the morning, when the British marched into Lexington, several dozen militiamen had formed under arms on the town's green. A tense standoff led to an exchange of fire that left a handful of militiamen dead, and the British columns continued to nearby Concord. Once there, they encountered stiff resistance, and they marched back to Boston through Lexington under almost constant attack from militiamen who had streamed in from the inflamed countryside. By the time they reached Boston, the British forces had suffered over 120 casualties, and the war that would result in American independence had begun.