This chapter takes up the debate within jus ex bello about the morality of continuing a war that has reached the limit of its ante bellum proportionality budget. The concept of proportionality implies some kind of equilibrium point between the value pursued and the disvalue created. Conceptions of proportionality in just war theory differ according to how that equilibrium point is understood and justified. This chapter sets out two different conceptions, the impersonal value conception and the personal value conception. The impersonal value conception expresses the ideal of equilibrium in the weights of commensurable impersonal value and disvalue. The personal value conception defines the equilibrium point by a principle that could be justified to those who might suffer and die in the war. I argue that the personal value conception is more restrictive of the harms that may be imposed both initially and when consider whether to continue fighting.

We are increasingly living in a world of forever wars, wherein neither party has a foreseeable determinate pathway to victory. This chapter explores three challenges for traditional just war theory raised by forever wars. First, I discuss and reject the claim that forever wars necessarily fail the proportionality and reasonable prospect of success conditions of jus ad bellum. Second, although forever wars may not be disproportionate, they do suffer from compounding errors and indeterminacy in assessing likely future costs and benefits. Finally, I consider time-variant value and discounting, wherein future goods are deemed to possess less value than present goods. Discounting is a feature of the appraisal of financial and monetary goods, and it seems to play a role in some moral judgements also. Subjecting the expected costs and benefits of war to discounting over time significantly impacts the moral permissibility of forever wars. Time variability impacts ad bellum judgements about the justification of war as well as in bello decisions, generating a reason to prefer weapons that generate immediate strategic advantage, but whose collateral costs often occur far in the future.