 Their pacifism left the Moriori unable to defend themselves when the islands were invaded by mainland Māori in the 1830s.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.