Do leaders learn more about military force from firsthand experience with the armed forces or their nation’s last war? Despite a resurgence of interest in the effects of leaders and their beliefs on international conflict and war, we still know little about which mechanisms cause what beliefs. I theorize that although personal experiences in the military may provide less normatively probative lessons for a leader contemplating the initiation of armed conflict than the nation’s last war, personal military experiences will have a greater impact on beliefs because they are directly experienced, cognitively accessible, and vivid. I argue that this availability bias should make leaders who have experience in the military but not combat operations develop beliefs that make them more likely to use force than leaders with combat experience. I test this hypothesis on the beliefs of John Kennedy and Lyndon Johnson with archival evidence and secondary studies. These cases control for the nation’s last war because both Kennedy and Johnson experienced the second World War but allow variation in military experience because Kennedy but not Johnson experienced combat. The results suggest that further attention to leaders’ personal military experiences will offer better predictions about their beliefs and foreign policies.