The twenty-two years of Saladin's rule, who is the founder of Ayyubid dynasty and the first sultan of Egypt and the Levant, witnessed tens of his battles against the Crusaders. Some of his battles happened against Muslim emirs in Egypt, the Levant, and Northern Iraq. The present paper, drawing on just war theory, aims to explore the findings of its historical study of the Islamic sources and some Christian research in order to provide an answer to the question of to what extent Saladin's military conduct and policies are compatible with the principles of just war. The results of this descriptive-analytical study indicate that Saladin's military conduct is more in line with the realistic theory of war rather than with the concept and principles of just war theory because while the latter consider just war a legal war to achieve peace by avoiding cruel treatment of civilians, prisoners, and the aggressed environments, Saladin has fought wars with the aim of attaining more dominance, accompanied by revenge and unconventional invasions destructive for the civilians. Therefore, in spite of his observance of ethical rules in many wars, cruelty and seeking power is observed in his other wars.