War is ... an act of force to compel our enemy to do our will

—Clausewitz, On WarCarl von Clausewitz, On War, ed. and tr. Michael Howard and Peter Paret, rev. edn (Princeton, NJ 1984), p. 75.

All politicians and national leaders are instinctive adherents of the formulation by Clausewitz cited above, even if few of them have actually read On War. Uninterested in — and often impatient with — military detail, fearful of casualties and expense, they are primarily concerned with the political result which a successful military action will bring, and often find professional realism about the efficacy of military power tiresome. In particular, the concept of military force exercised or threatened to bring about the political collapse of a state, or the destruction of the morale of its people, or even a modification in the policies of its government, is a habitual policy of national leaders, and has been for many years a commonplace in that grey area where the concerns of politicians and military men overlap. In this article, I show by historical example how difficult the use of military power in this way has been, and how unclear it is whether there is any straightforward way in which military force can be calibrated and employed, or threatened, for political ends.