Musket Wars
Thousands of Maori died in the intertribal Musket Wars of the 1810s, 1820s and 1830s. Many more were enslaved or became refugees. Northern rivals Ngapuhi and Ngati Whatua led the way, but all the tribes were soon trading for muskets.
Muskets (ngutu parera) changed the face of intertribal warfare, decimating some tribes and drastically altering the rohe (territorial boundaries) of others. By the 1830s campaigns had become too costly. With European diseases also taking a heavy toll, warfare gave way to economic rivalry.
https://nzhistory.govt.nz/war/new-zealands-19th-century-wars/the-musket-wars