To prevent Howe's forces in Philadelphia being resupplied by sea, the Patriots erected Fort Mifflin and nearby Fort Mercer on the east and west banks of the Delaware respectively, and placed obstacles in the river south of the city. This was supported by a small flotilla of Continental Navy ships on the Delaware, supplemented by the Pennsylvania State Navy, commanded by John Hazelwood. An attempt by the Royal Navy to take the forts in the October 20 to 22 Battle of Red Bank failed; a second attack captured Fort Mifflin on November 16, while Fort Mercer was abandoned two days later when Cornwallis breached the walls. His supply lines secured, Howe tried to tempt Washington into giving battle, but after inconclusive skirmishing at the Battle of White Marsh from December 5 to 8, he withdrew to Philadelphia for the winter.