One of the few stylized facts in international relations is that democracies, unlike autocracies, almost never fight each other. Recent empirical findings show that binding term limits invalidate this result: democratic dyads in which at least one country imposes term limits on the executive are as conflict prone as autocratic and mixed dyads. Moreover, in democracies with two-term limits conflicts are more likely during the executive's second term. To rationalize these findings, we model international relations as a repeated prisoners' dilemma. We show that the fear of losing office makes democratic leaders less willing to start costly conflicts. Crucially, this discipline effect can only be at work if incumbent leaders can run for re-election. Term limits thus make it harder to sustain peaceful relations.