In 1916 conscription for military service was introduced to maintain New Zealand's supply of reinforcements. More than 30,000 conscripts had joined the New Zealand Expeditionary Force by the end of the war.
In his recruitment waiata, 'Te ope tuatahi', Ngata made it clear that the replacement recruits that he and his colleagues had raised all came from the East Coast tribes of Mahaki, Hauiti, Ngati Porou, Te Arawa and Kahungunu.
Peter Fraser's trial at the Wellington Magistrates' Court was the sequel to an anti-conscription speech. A number of union leaders were charged with the same crime. Fraser was convicted and served 12 months in gaol.