The escalation of violence in the late 1820s prompted Lieutenant-Governor George Arthur to declare martial law—effectively providing legal immunity for killing Aboriginal people[7]—and in late 1830 to order a massive six-week military offensive known as the Black Line, in which 2200 civilians and soldiers formed a series of moving cordons stretching hundreds of kilometres across the island in order to drive Aboriginal people from the colony's settled districts to the Tasman Peninsula in the southeast, where it was intended they would remain permanently confined.[8][9][10]