States and empires adopted a combination of other approaches targeting the strengths of barbarian groups. First, the construction of frontier fortifications combined with the development of local forces tried to stabilize the immediate 1 Cited in Paul Beck, Columns of Vengeance (Norman, OK: University of Oklahoma Press, 2013), 247. 2 On commercial relations with nomadic tribes, see for instance, Khodarkovsky, 26-8 (for Russian and the steppe tribes); Frederick Mote, Imperial China, 900-1800 (Cambridge, MA: Harvard University Press, 1999), 692-3 (on Ming China’s relations with the Mongols). frontier separating the polity from the barbarians. Second, great powers from Rome to the United States saw the high mobility of the barbarian tribes as a key source of their threatening power, and sought to limit it by settling them down. Finally, third, often the long-term strategy was to alter the environment that allowed barbarian groups to prosper. The empty or ungovernable spaces – the steppes, the deserts, the difficult to conquer forests – had to be dominated through technology and the gradual expansion of state institutions, thereby limiting the area where barbarians could move unhindered.