Kukutai and Wiremu Te Wheoro assisted British forces in the military invasion of the Waikato in July 1863, building and occupying a pa at Te Ia, (near Mercer) and transporting supplies for the British from steamers at Waikato Heads upriver to the Camerontown redoubt, until the supply line was severed by a Ngati Maniapoto attack in September. Kukutai fought with the Kingitanga forces at Rangiriri in November 1863. He was appointed as a major in the New Zealand militia.