Pirates operating from Aceh threatened commerce in the Strait of Malacca; the sultan was unable to control them. Britain was a protector of Aceh and gave the Netherlands permission to eradicate the pirates. The campaign quickly drove out the sultan but the local leaders mobilized and fought the Dutch in four decades of guerrilla war, with high levels of atrocities. The Dutch colonial government declared war on Aceh on 26 March 1873. Aceh sought American help but Washington rejected the request.