To settlers on the borders of the advancing Western frontier, the plains Indians were terrorists. To the US military, they were a powerful insurgent force. Red Cloud had led a successful campaign against US forces that resulted in the closing of the Bozeman trail. He then settled down as did his followers. As Crazy Horse, Gaul and Sitting Bull continued to emerge as powerful war leaders, they were able to pull many recruits north who participated at Rosebud and Little Big Horn. Many of the same recruits/volunteers subsequently returned to the reservations and secured areas. Crazy Horse and Sitting Bull and their bands kept on the move. Said bands and their number of fighting men were relatively small in number compared to availbable numbers at the time of the two previously mentioned big fights. History would suggest that when Zaqawri was at his peak, there was likewise a peak in number of active and tacit supporters. I see these stats, the attempts at making a head count or terrorists per se, as very murky and fluid at best. This murkiness gives some justification IMHO for the population-centric approach in counterinsurgency in the Iraq theatre of operations.