This paper explores the military aspect of the Arab Spring, and specifically the role played by formal armies in the Arab Spring states. Specifically, this paper focuses on the fact that popular revolutions during the Arab Spring were successful in those countries in which the military sided with the protestors, whereas revolutionary momentum could not face down the regimes in those countries where the armies did not side with the revolution. The political functions which Arab armies carry out serve to highlight not only their significance and effectiveness as institutions, but also the need for military reform. The question of military and security sector reform has become increasingly pressing in the post-Arab Spring transitional phase, driving the author to probe the structural aspects of reform to the military and security sectors of the Arab Spring states.