The "tusi" were considered vassals of the Ming emperor. They enjoyed autonomy or semi-autonomy in their domains, but were expected to maintain order and defend the border zones for the Ming dynasty. When the Ming court wanted to start any campaign near their domains, the chieftains were required to lead their private armies and assist the Ming army in the battle. Those soldiers supplied by "tusi" were called "Tu Bing" ("native soldier"). In the campaign against Annam, the Ming court recruited a large number of native soldiers from the southern provinces.