Saddam's Iraq has become a cliché in the study of military effectiveness—the quintessentially coup-proofed, personalist dictatorship, unable to generate fighting power commensurate with its resources. But evidence from the later years of the Iran-Iraq War actually suggests that the Iraqi military could be quite effective on the battlefield. What explains this puzzling instance of effectiveness, which existing theories predict should not have occurred? Recently declassified documents and new histories of the war show that the Iraqi improvements stemmed from changes in Saddam's perceptions of the threat environment, which resulted in significant shifts in his policies with respect to promotions, training, command arrangements, and information management in the military. Threat perceptions and related changes in these practices also help explain Iraq's return to ineffectiveness after the war, as evident in 1991 and 2003. These findings, conceived as a theory development exercise, suggest that arguments linking regime type and coup-ridden civil-military relations to military performance need to take into account the threat perceptions that drive autocratic leaders’ policies toward their militaries. After discussing how to define and measure battlefield effectiveness, the article reviews Saddam's changes and their effects; addresses alternative explanations for the improvement in Iraqi effectiveness; and explains how further research based on this initial exercise could generate a better understanding of the observed variation in states’ battlefield effectiveness, including variation within and across autocratic regimes.