This thesis tests Arash Heydarian Pashakhanlou’s Underdog’s Model (UM) of asymmetric airpower through a structured, focused comparison of the 1940 air campaigns in the Battle of France and the Battle of Britain. Using an evidence matrix and relative within-case assessments of the relatively disadvantaged belligerent in each campaign, it evaluates performance across six interlinked dimensions: creativity; self-sufficiency and external support; commitment; intelligence; dispersion and concentration; engagement of vulnerable military targets. In France, the Armée de l'Air underperforms its opponent on five dimensions (with commitment roughly equal), consistent with underdog failure to deny the opponent’s objectives. In Britain, the Royal Air Force outperforms its opponent on five dimensions (but underperforms on dispersion and concentration), consistent with successful denial. Overall, the study offers tentative support for UM’s holistic, probabilistic logic, while noting limits to inference from two cases and qualitative coding.