Since the mid-1800s, clergy, doctors, other clinicians, and military personnel who specifically facilitate their work have been designated “non-combatants”, protected from being targeted in return for providing care on the basis of clinical need alone. While permitted to use weapons to protect themselves and their patients, they may not attempt to gain military advantage over an adversary. The rationale for these regulations is based on sound arguments aimed both at reducing human suffering, but also the ultimate advantage of the nation-state fielding non-combatant staff. However, this is sometimes not immediately apparent to combatant colleagues. Clinicians in the armed force are also military officers, owing a “dual loyalty” that can create conflict if their non-combatant status is not well understood. Historical examples of doctors breaching their responsibilities include prioritisation of combat capability over the rights of individual soldiers (as occurred when scarce medical resources were allocated to soldiers more likely to return to battle in preference to those most likely to die without them), use of physicians to facilitate prisoner interrogation, medical research or treatment to enhance physical performance at the expense of health, application of Medical Rules of Eligibility according to factors other than clinical need, provision of treatment contingent upon support for military objectives, and use of medical knowledge to enhance weapons. However, not being a combatant party to a conflict does not imply that the non-combatant clinician cannot act in the national interest. Indeed, by adhering to the same universal ethics as their civilian colleagues, military clinicians provide optimal care to their own troops, facilitate freedom of action in host nations, and build positive international relationships during the conflict and in the post-conflict state.