The Almoravids as one of the most important Islamic states in the fifth century AH (the eleventh AD), after consolidating power and establishing legitimacy, ruled Maghreb and Andalusia. They first formed the movement in the Sahara and then succeeded to establish a government by careful planning and changing the military organization. On the one hand, supremacy over the various Maghreb tribes and domination over them, and the presence in Andalusia and jihad against the Christians, on the other hand, led to the formation of the Almoravids political power. Therefore, the analysis of the role of the evolutions and organization of the Almoravids in the establishment of their rule has been considerably important. Accordingly, the present study with a descriptive-analytical approach and by emphasizing the sources about and of this period tried to investigate the causes of the formation of the military power of the Almoravids and the changes they made in the military organization. The findings indicate that the Almoravids initially exploited the Maghreb's capacity for hegemony of power and established their sovereignty. Then they reformed the structure of the army and advanced to Andalusia for jihad. At this stage, they developed and innovated the army, and planned for various battles.