The H. M. S. ' Augusta' Philadelphia -1777- Artist: ęGeoff Hunt British 64-gun ship under fire from Fort Mifflin and Pennsylvania State Navy gunboats. In October 1777 the British Royal Navy tried to force its way up the Delaware River to make contact with their army, then occupying Philadelphia. The State of Pennsylvania had organized a strong defense using underwater obstacles, shore forts, and a purpose-built gunboat navy. But on 23rd October it was