Under Hongi Hika's command, Ngāpuhi began amassing muskets and from about 1818 began launching effective raids on hapu throughout the North Island against whom they had grievances. Rather than occupy territory in areas they defeated their enemy, they seized taonga (treasures) and slaves, who they put to work to grow and prepare more crops—chiefly flax and potatoes—as well as pigs to trade for even more weapons. A flourishing trade in the smoked heads of slain enemies and slaves also developed.