Dartmouth Castle is an artillery fort, built to protect Dartmouth harbour in Devon, England. The earliest parts of the castle date from the 1380s, when, in response to the threat of a French attack, the civic authorities created a small enclosure castle overlooking the mouth of the Dart estuary. This was intended to engage enemy ships with catapults and possibly early cannon, and incorporated the local chapel of Saint Petroc within its walls. At the end of the 15th century, the castle was expanded with an artillery tower and an iron chain which could be stretched across the harbour to a tower at Godmerock; this addition formed the oldest known purpose-built coast artillery fort in Britain. Further gun batteries were added during the French invasion scare of the 1540s.