War is always hell, but it is not always immoral. As military historian Frederick Kagan points out in a charming piece in the new Wilson Quarterly, a nation must always be willing to use force to attain its national goals: 

“‘You have no idea how much it contributes to the general politeness and pleasantness of diplomacy when you have a little quiet armed force in the background,’ the diplomat-historian George F. Kennan declared in 1946. With his customary wit, Kennan enunciated a profound general principle: War and diplomacy are inextricably linked, and it is as great a mistake to conduct diplomacy without considering military means as it is to wage war without diplomacy.

“This truth has never enjoyed universal acceptance, but in modern times the conviction-or wish-that diplomacy can prevail without any connection to the use of force has become much more widespread. Many see war simply as the failure of diplomacy rather than its complement, and some argue that statesmen should not even consider using military power until they have exhausted all other means of achieving their aims. It is not only the evil of war that animates these critics, but the belief that force makes any kind of diplomacy all but impossible-that the angry ‘blowback’ of elite and popular opinion in other nations necessarily overwhelms all diplomatic efforts, traditional or public, and outweighs any advantages that force may bring. ‘Hard’ power and ‘soft’ power, in other words, are mutually exclusive.”

Kagan admits that use of force against an insurgency such as the one the U.S. faces in Iraq can be a more complicated matter, but those who say that is impossible to win in such a conflict are wrong-the English, for example, prevailed over the Boers through a greater (and to me sometimes highly disturbing) use of force and yet the two nations went on to fight side by side in later conflicts.

Kagan writes: 

“The existence of a powerful and battle-proven military makes the job of diplomats and political leaders vastly easier. However unhappy a defeated people may be with a given political settlement, or however resentful of military actions carried out against them, very few will take up arms again if convinced that they will  again be defeated. Military half-measures designed to ‘send a message,’ such as those the Kennedy and Johnson administrations used in the early days of the Vietnam struggle, deceive no one and leave the door open for insurgent victory. Clear-cut military triumph, such as the British achieved against the Boers, makes even the staunchest rebels more reluctant to try the test of battle again. The use of military force with any aim in mind other than victory is extremely dangerous and likely to be counterproductive.”