But with the arrival of a third hapu of the Ngati Kahungunu, the Ngāi Tahu (or Kaitahu), towards the close of the 17th century, the stormy era of Otago history began. Again it has been said that the desire to possess unlimited supplies of the precious "pounamu" or greenstone, which occurred only in the South Island, provided a powerful incentive for invasion. But this has been questioned. The combatants don't fall neatly into groups of Kati Mamoe and Kai Tahu and the given reasons for strife don't refer to greenstone. Hostilities were protracted and Kati Mamoe were never "subdued". There were still people of that descent living in the region when the first Europeans arrived and Kai Tahu were just another Māori people also living in the south.