Sailors from USS Constitution march through the streets of Charlestown followed by Navy Band Northeast during the Bunker Hill Day parade. The Battle of Bunker Hill, fought, June 17, 1775, was one of the first major engagements of the Revolutionary War. Colonial forces inflicted 1,054 casualties on the British, the highest suffered by the British in any single encounter during the entire war. The Colonial forces suffered 450 casualties. most suffered during an orderly retreat to fortified positions in nearby Cambridge.