Luttwack's thesis, that late Republican and early Imperial Rome had a deliberate long-range grand strategy that dictated the siting of its frontier defenses, was challenged in 1991 by Israeli classicist Benjamin Isaac's The Limits of Empire. Isaac, in essence, claimed that Roman frontier defenses were not set in accordance with a phased plan of conquest, but in order to control ambivalent populations along the fringe areas and to ensure non-interference from the outlanders. The debate, unusually heated for classicists, has on the whole tended to bolster Luttwack somewhat in arguing for a rational "forward defense" policy. Luttwack's original thesis (1976) was written with contemporary US defense planning in mind; how to spread sparse post-Vietnam American assets so as to most efficiently check Soviet agressive designs. Although Luttwack has generally declined to revisit his Roman tour de force, (he is currently working on a strategical analysis of the Byzantine Empire), it is still a thought-provoking handy review of how Rome pursued a containment policy in the teeth of severe budgetary restraints.