《明史·志·卷六十五》
四卫营，永乐年间，让从北方逃回来的军士供养马役，供给粮饷授予房屋，号称勇士。
四卫营者，永乐时，以迤北逃回军卒供养马役，给粮授室，号曰勇士。
In the Yongle era, the Four Guards Camp let the soldiers who fled back from the north work as grooms, provided rations and housing, and called them warriors.