This paper is a comparative study of the sources of the current changes of military doctrines in the Middle East, using process-tracing and qualitative methods (See John Gerring, Case Study Approach, 2007). Case studies are Iran, Israel and Saudi Arabia, which represent major, militarily-active powers in the region, that employ large, modern military organizations, and at the same time exhibit significant variance in factors that influence the choice of military doctrine. It illustrates how the three countries – though reacting differently to the evolving post-Arab Spring systemic threats – share the common denominator of adopting more offensive doctrines (See the "Israel Defense Forces Strategy," 2015; Khaled Al-Faisal, “A Saudi Defense Doctrine for a New Era,” 2015; Erik Olson, “Iran’s Path Dependent Military Doctrine,” 2016). It then moves to explain these doctrinal changes through testing hypotheses derived from the three established theoretical perspectives on the sources of military doctrine: balance-of-power theory, organization theory and cultural theory (See Barry Posen, "The Sources of Military Doctrine," 1984; Jack Snyder, "The Ideology of the Offensive," 1989; Elizabeth Kier, "Imagining War," 1997). The analysis reveals that while systemic imperatives are influential, they are not determinants of doctrinal change, which is a function of each state’s political culture and interests of its military organization(s). The Israeli doctrine, though it remains essentially offensive, included an important element of defense, due to a combination of hesitant political leadership and over-casualty sensitive public. The Saudi doctrine shifted from its traditional defensive character to an offensive one for the assertive ambitions of the new political leadership, embodied in the young Crown Prince. The Iranian doctrinal emphasis on offensive is attributed, at lease partly, to the institutional rivalries between the conventional military and the Revolutionary Guard. The paper presents a more complex reality than the one portrayed by conventional wisdom in the literature on Middle East military doctrines that mostly misperceives the subject country as a unitary actor whose choice is based solely on systemic factors. The paper therefore offers insights for important theory and policy recommendations.