Nuku, said to have been called Nuku-pewapewa because his moko was in the style called pewapewa, was born probably in the late eighteenth century, in Wairarapa. He was descended from the ancestors Kahungunu, Rangitane, Te Aomatarahi and Ira. His principal hapu was Ngati Kahukura-awhitia. Some genealogies suggest that Nuku-tumaroro was his father. It is more likely that he was the son of Te Ono, Nuku-tumaroro's second son, and his wife, Parahako. Earlier biographies have attributed to him the warlike exploits of an ancestor, also called Nuku, who lived five generations before. Both men exhibited ingenuity and skill in war; this could have helped to cause the confusion.
Nuku-pewapewa was a prominent leader in the period of disturbance between 1820 and 1839, when wars and migrations caused upheaval among the peoples of both islands. About 1820 a war expedition from the north, led by Tuwhare, Patuone, Nene and others, reached Wairarapa. The war party possessed muskets, a new weapon to which the old name, pu, a traditional war trumpet, had been given. When Nuku-pewapewa learned that Tuwhare and his allies were coming armed with pu, he is said to have replied: 'Let them come, let them blow their pu; my men can also blow pu.' Many war trumpets were sounded as the enemy approached, but their pu were muskets and many of Nuku-pewapewa's people were shot.
The next day he set up an ambush and captured three muskets and some of the marauding party. He tried to get the prisoners to show him how to use the new weapons, but they tricked him by loading them incorrectly. When the muskets would not fire, the prisoners explained that they were tapu and would only fire when aimed to kill. Nuku-pewapewa then tried them out against Rangitane of the Moawhango district, but they still would not work. He abandoned them, and won a victory using traditional weapons.
Tuwhare's expedition went to Te Whanganui-a-Tara (Wellington Harbour) and then to Porirua. There Nuku-pewapewa attacked them, and regained his mana by capturing Te Ata-o-te-rangi, Taunuha, Korewa and six others. This victory enhanced his reputation, and he was invited to Heretaunga (Hawke's Bay) by Te Pareihe, the war leader of Ngati Te Whatu-i-apiti, to help 'extinguish the fires' kindled at Te Roto-a-Tara by an invading force led by Mananui Te Heuheu Tukino II of Ngati Tuwharetoa.
At this time Te Pareihe wanted the Heretaunga people to withdraw to Nukutaurua, on the Mahia peninsula, because his tohunga, Ngoi, had predicted massive invasions of Hawke's Bay. But many refused to go. While the departure was being discussed by the people of Heretaunga, collected together in the pa Tane-nui-a-rangi, Nuku-pewapewa and the Wairarapa refugees arrived at Waimarama. There they built the pa Te Putiki. The Heretaunga leaders Te Moananui and Te Hapuku wished to attack them, but the Waimarama elder Tuaha rebuked his relatives: 'When will it be the time for compassion?'
Nuku-pewapewa withdrew with Te Pareihe to Nukutaurua. There they lived for some years, in partnership with Te Wera Hauraki and his Nga Puhi people. They built up their supplies of muskets by trading with American whalers, and became involved in the East Coast wars of the 1820s. Nuku-pewapewa, with Te Pareihe, helped Te Kani-a-Takirau of Ngati Porou take vengeance against Te Whakatohea and Ngai Tai for the killing of a Rongowhakaata man. In spite of receiving valuable gifts (including a fine war canoe) from Te Kani-a-Takirau, Te Pareihe was doubtful about going to his aid. When asked for his opinion, Nuku-pewapewa replied in words which have become famous: 'Never turn back when the voice of war is sounding in your ears.'
Nuku-pewapewa accompanied Te Wera Hauraki and Te Pareihe in a major punitive raid against Mananui Te Heuheu. The expedition consisted of 1,600 warriors; it overthrew the pa at Omakukura, on the north-west side of Taupo, killing at least 400 people. Peace was arranged by Te Rohu, the daughter of Mananui. While Te Pareihe and Nuku-pewapewa were involved in war on the east coast, news arrived that Te Momo-a-Irawaru of Ngati Te Kohera, a hapu of Ngati Raukawa, had occupied Te Roto-a-Tara. Te Pareihe, Te Wera Hauraki and Nuku-pewapewa led a force which succeeded in taking Te Roto-a-Tara by storm. Te Momo was killed nearby at Kahotea, and his attempt to occupy southern Hawke's Bay thus failed. Later, news came to Nukutaurua that Te Whatanui of Ngati Raukawa, with Rangitane allies, had invaded Hawke's Bay through the Manawatu Gorge, killing several chiefs, in order to avenge the death of Te Momo-a-Irawaru. Nuku-pewapewa and Te Pareihe led a war party to punish Ngati Raukawa and Rangitane. A battle took place at Te Ruru, near present day Dannevirke; the eastern sections of Rangitane were the main victims.
While Nuku-pewapewa was away from Wairarapa, the district was invaded again, this time by the Taranaki peoples Te Ati Awa, Ngati Tama and Ngati Mutunga. After the defeat of the Wairarapa people at Pehikatea about 1833, the majority went north to Nukutaurua. Although the accounts which have been preserved are conflicting, it is most likely that Nuku-pewapewa heard of the fresh invasion from refugees arriving at Nukutaurua, and began to plan to expel the invaders.
Although he was warned not to go, Nuku-pewapewa led a Wairarapa force of 200 to Maungaraki, a range south-east of present day Masterton. He was accompanied by Te Hapuku, leading a force of 400 Heretaunga men. The leaders climbed a hill at night and saw the innumerable fires of their enemies. Except for a few, led by Hoeroa of Ngati Te Upokoiri, the Heretaunga forces withdrew. In spite of this defection, Nuku-pewapewa took by surprise the pa at Tauwhare-rata (near present day Featherston), where Te Wharepouri, the leader of Te Ati Awa, was living.
Te Uamairangi and Te Kakapi, the wife and the adoptive stepdaughter of Te Wharepouri, were captured, with 25 others. Nuku-pewapewa spared the lives of the captives, and sent Te Uamairangi to her husband, in an effort to make peace. In response Te Uamairangi presented Te Kakapi to Nuku-pewapewa. This laid the basis for the peace that was later concluded. Nuku-pewapewa returned, with Te Kakapi, to the north.
After these battles Te Wharepouri went north to negotiate the return of his niece and adopted daughter. The price was to be the restoration of Wairarapa to its dispossessed people. However, Nuku-pewapewa was not there to arrange the peace. He had been travelling south as Te Wharepouri sailed north. At Tahaenui, between Nuhaka and Whakaki, near Wairoa, his canoe overturned in the mouth of the river; a wave lifted the canoe above him and it struck him on the head, killing him.
Peace with Te Wharepouri was made by Pehi Tu-te-pakihi-rangi, and beginning in 1841 the Wairarapa people returned to their homes. Through the efforts, valour and wisdom of Nuku-pewapewa the mana of the Wairarapa people was preserved. His canoe was carved and erected as a monument at Whakaki. A carved figure representing him was built into the palisade at the Papawai marae near Greytown.