Air power alone cannot hold ground and secure the population. How then can air power contribute to irregular conflicts? Robert Johnson states in his article Predicting Future War that air power have the potential to determine the outcome of irregular operations. Even though air superiority was achieved during the two battles of Fallujah in Iraq 2004 there is a difference in the outcome of the two operations, Vigilant Resolve and Phantom Fury. The purpose of this thesis is to examine if Warden´s theory The Enemy as a System and his Five-Ring Model can explain the variation in the outcome of the two battles using a comparative case study. Research findings indicate that the Five-Ring Model cannot explain why the second operation, Phan-tom Fury was a victory. The findings indicate that striking the most critical ring, i.e. Leaders, did not contribute to victory. Instead, results indicate that the most critical ring leading to victory in the second operation were Infrastructure. The main conclusion of the thesis is that the theory cannot explain the variation in the outcomes and that Warden´s Five-Ring Model cannot be applied to an irregular enemy and therefore needs to be questioned and further researched. The findings further strengthen earlier research stating that the most critical part of an enemy may not always be represented by Leaders.