Mao's confidence in military confrontations with more powerful adversaries continues to inspire Chinese strategists more than half a century later. This article explores the origins and development of Mao's thinking in this regard, focusing particularly on his years in Yan'an. Drawing on newly available sources, the analysis stresses the importance of experience, as opposed to ideology, in the development of Mao's martial confidence. For much of his time in Yan'an Mao was relatively circumspect in his military ambitions. Yet towards the end of this period his confidence rose considerably after successes against the KMT offensive in 1946. In short, Mao's martial confidence did not spring fully formed from his ideological convictions but emerged over time.