This chapter shows that, under the Pahlavi monarchy, the country had one of, if not the, best-equipped and best-trained military in the Middle East and North Africa region. In this chapter, the focus is on how the Imperial Armed Forces changed following the revolution. Attention is drawn to the structure of the Islamic Republic’s military machine and to the historical and strategic forces that have come to determine the shape, doctrine, and capabilities of the country’s armed forces. The impact of the revolution itself on the armed forces was significant, compounded by the role-defining war with Iraq (1980–8). As a consequence of developments since 1979, the Sepah has emerged as the republic’s most powerful fighting force, the establishment’s trusted weapon against domestic dissent, and the regime’s leading weapon in regional conflicts. This centrality is largely attributed to the IRGC Command Network.