In 1596, the Dutch made a first unsuccessful attempt at capturing the castle, succeeded by a successful one in 1637, after which it was made the capital of the Dutch Gold Coast. During the period of Dutch control, new, smaller fortress were built on a nearby hill to protect St. George's Castle from inland attacks; this fort was called Fort Coenraadsburg. The Dutch continued the triangular Atlantic slave route until 1814, when they abolished the slave trade, pursuant to the Anglo-Dutch Slave Trade Treaty.