ABSTRACT
The effective defence of the empire by war and diplomacy naturally depended both on imperial unity and stability, and on a total resource base of manpower and wealth. At a period when the external threat was graver than ever, the state’s total tax burden was very many times greater than in the earlier, more secure empire of Vespasian or Hadrian.1 In that vanished period the newly pacified provinces could still be parted from much of their indigenous wealth, to the benefit of the Italian heartland and the older provinces, so that both actual and perceived taxation was modest, at least among the classes who counted. Although that empire had fought its wars, it had not been required to face continuous war, decade after decade, on two great frontiers simultaneously; nor was it equipped for it.
