Editing Fort Mifflin (section)

== Colonial Construction ==

The British recognized the strategic importance of controlling the Delaware River approaches to Philadelphia and began constructing fortifications on Mud Island in 1771. The site, a low marshy island approximately 200 yards from the Pennsylvania shore, commanded the main shipping channel and could subject passing vessels to cannon fire. The British built an earthwork fort with wooden palisades and mounted cannon to protect Philadelphia from naval attack. The fort remained incomplete when the American Revolution began, and British forces abandoned it as Pennsylvania patriots took control of the colony's military resources. American engineers, including Polish volunteer Thaddeus Kosciuszko, strengthened and expanded the defenses in preparation for the conflict to come.<ref name="mcguire">{{cite book |last=McGuire |first=Thomas J. |title=The Philadelphia Campaign, Volume II: Germantown and the Roads to Valley Forge |year=2007 |publisher=Stackpole Books |location=Mechanicsburg, PA}}</ref>

The American defensive system on the Delaware combined Fort Mifflin with Fort Mercer on the New Jersey shore and an extensive network of underwater obstructions called chevaux-de-frise—sharpened logs anchored to the river bottom to tear the hulls of ships attempting to pass. The Pennsylvania State Navy, a force of armed galleys and floating batteries, provided mobile firepower to supplement the fixed defenses. Together, these elements created a formidable barrier that any British force approaching Philadelphia by water would have to overcome. The strength of the Delaware defenses would be tested severely in the fall of 1777.<ref name="jackson"/>