Two Taranaki tribes, Ngati Tama and Ngati Mutunga, displaced by the Musket Wars, carried out a carefully planned invasion of the Chatham Islands, 800 km east of Christchurch, in 1835. About 15% of the Polynesian Moriori natives who had migrated to the islands at about 1500 CE were killed, with many women being tortured to death. The remaining population was enslaved for the purpose of growing food, especially potatoes. The Moriori were treated in an inhumane and degrading manner for many years. Their culture was banned and they were forbidden to marry.