Military endeavours, and especially knightly duels, are the most frequent narrative element in the Lancelot propre, central romance of the Lancelot-Graal cycle. Their outcome is usually decided by the combatants’ value but, in various instances, an element of mischief is crucial. Reading the text following the theme of the ruse - which appears even in one of its first scenes - elicits a long list of questions: first of all because of its moral ambiguity, sometimes difficult to understand completely because of the chronological vagueness of the Lancelot propre and our scarce knowledge of the relevant military conventions. Additionally, narrative mechanisms and characters’ definition in the romance also contribute to its difficult understanding. Some relevant examples show how the ruse is present in both individual and collective military confrontations, usually with a negative characterization that derives from the moral code set out in the text for knights.