This study is an analysis of expeditionary air base defense in the post-World War II era, focusing on Western military examples, with the goal of informing current and future leaders within the USAF and larger joint military force. The study begins with a brief overview of the contemporary operational environment and likely future trends in the threats to US expeditionary air bases. A concise comparison of USAF air base defense forces from the 1960s and the 2010s follows, highlighting the increase in training quality and competence, and the decrease in organic weapons capability. A series of case studies examines the defense of Dien Bien Phu by the French in 1954, Khe Sanh, Tan Son Nhut, and Bien Hoa by US Forces in the 1964-1972 period, the US coalition at Joint Base Balad during Operation Iraq Freedom, and the NATO coalition at Bastion-Leatherneck-Shorabak during Operation Enduring Freedom in 2004-2012. Analysis of these case studies reveals several themes of expeditionary air base defense in the modern era, including: the pervasive problem of standoff indirect fire attacks; the criticality of a competent and dedicated ground intelligence function, and its conspicuous absence; the importance of supporting fires; and, the tendency to underestimate enemy forces. The paper concludes by arguing that the Department of Defense should persist with and strengthen recent positive changes to Joint Doctrine. The Base Security Zone of expeditionary air bases should be identified as part of a terrain and threat analysis, and used to set the Base Boundary to enable effective base defense operations led by a single commander at the appropriate tactical level. Dedicated intelligence support, effective cross-functional base planning, from site selection to base layout, construction, and operation, and unity of effort and detailed integration of joint forces are critical elements.