War is the existential negation of the enemy.

If there is a political realm then it is based in the distinction between friend and enemy, much as ethics is the distinction between good and bad and aesthetics is the distinction between beautiful and ugly. Thus (Schmitt 1996, p. 35)

Schmitt 1996

A world in which the possibility of war is utterly eliminated, a completely pacified globe, would be a world without the distinction of friend and enemy and hence a world without politics. It is conceivable that such a world might contain many very interesting antitheses and contrasts, competitions and intrigues of every kind, but there would not be a meaningful antithesis whereby men could be required to sacrifice life, authorized to shed blood, and kill other human beings.

At first Schmitt appears to present an enlightened and pragmatic view of war: ‘…it would be senseless to wage war for purely religious, purely moral, purely juristic, or purely economic motives’ (p. 36). The catch, however, is that non-political situations can become political. Religious, moral and economic antitheses can intensify or contribute to the political antithesis of friend and enemy. So although Schmitt’s position appears at first to ridicule religious, moral or economic wars, his definition of war does not permit of a war that is not political. ‘War is the existential negation of the enemy’, and it is not possible to existentially negate another without that other being by definition an enemy (p. 33). Schmitt’s definition of war and criteria of the political are therefore circular: (1) the criteria of friend and enemy define ‘the political’; (2) war is the existential negation of the enemy; (3) therefore, all war is political.