This paper examines how the context of civil war in the Anglo-Norman and Angevin realms c. 1100–c. 1216 might further accentuate the challenges faced by leaders in making the critical decision as to whether to avoid or to commit to battle. Whereas a commander confronting an external opponent might withdraw or refusal battle until a more advantageous moment presented itself, a ruler whose legitimacy was contested could ill-afford to harm his authority by being seen to refuse trial by battle. If defeated, however, such authority could be gravely undermined and, as shown by the case of King Stephen's capture in 1141, the sacrality of kingship itself damaged. Conversely, while victory would bolster prestige and legitimacy, as well as striking a potentially decisive blow to rival forces, a leader's own desire to give battle might be compromised by fear of disloyalty and defection before or during battle, or thwarted by the nobility's deep-rooted reluctance to engage in a potentially self-destructive combat. While many nobles shrank from fighting against the person of the king during rebellion, battles fought in the context of civil wars reveal the significance of disinherited magnates in aggressive attacks upon their erstwhile lords.