‘Operational incidents’ denotes misconduct, misdeeds or mishaps that occur on military operations, whether concerning the mistreatment of enemy soldiers, offences against civilians, conflict of varying levels within one’s own forces, or accidents that lead to injury or death within a theatre of operations. Alleged breaches of IHL or the disciplinary regulations of particular militaries require at the very least an initial assessment to determine the facts and then, if warranted, a more substantial investigation. The need for robust investigations, however, is not always matched by the will and the ability to undertake them. There is at last a sufficient body of experience on which we can reflect, in this volume, on such investigations, their challenges, and their likely evolution.