On October 18, General Sir William Howe, the commander of the British Army, evacuated his camp at Germantown and pulled his forces inside the city of Philadelphia. He sent a part of his force to capture the two American forts denying him use of the Delaware River. Earlier, Howe had sent a group of men via Webb's Ferry, at the mouth of the Schuylkill River, to marshy Providence Island (actually on the Pennsylvania mainland by Mud Island) to construct artillery batteries to bombard Fort Mifflin. The first bombardment of Fort Mifflin came on October 11. This was merely a desultory attack which convinced the British to expand and improve their batteries.