We develop a dynamic model to study how a patron state’s leadership turnover affects its protégé’s war decision against a common aggressor. Anticipating future reduced support from her successor, the incumbent leader of the patron state is incentivized to increase support to encourage the protégé to escalate. A successful escalation improves the issue’s division for both the patron and the protégé, while a failure worsens the status quo, pressuring the successor to provide support they might otherwise withhold. We illustrate this theory with the Biden administration’s landmark decision to allow Ukraine to attack Russian territory with U.S. weapons following Donald Trump’s election as president. This study sheds light on the interplay between domestic politics and extended deterrence.