UC San Diego

According to a leading rationalist explanation, war can break out when a large rapid shift of power renders unbelievable a rising state's promise to compensate its declining opponent, causing the latter to attack preventively. This mechanism does not provide a complete and coherent explanation of war because it does not specify how inefficient fighting resolves this commitment problem. We present a complete information model of war as a sequence of battles and show that although opportunities for a negotiated settlement arise throughout, the very desirability of peace creates a commitment problem that undermines its likelihood. Because players have incentives to settle as soon as possible, they cannot credibly threaten to fight long enough if an opponent launches a surprise attack. This decreases the expected duration and costs of war and causes mutual deterrence to fail. Fighting's sheer destruction improves the credibility of these threats by decreasing the benefits from continuing the war. Equilibrium fighting may involve escalating costs that exceed the value of the stakes by the time peace is negotiated and that leave both players worse off than when the war began.