Following the capture of Philadelphia by British forces in 1777, Continental Army troops and the Pennsylvania State Navy fought to prevent the Royal Navy from sailing up the Delaware River. After several weeks of fighting, the British bombarded Fort Mifflin with a massive cannonade. The troops held out for as long as they could, but finally on the night of Nov. 15, 1777 the garrison was evacuated by boat. In this episode of It's History, we visit today's Fort Mifflin and tell the story of the battle.