In cases of suspected violations of rules, regulations or the law by armed forces personnel, investigations are invariably mandatory. Military investigations differ from well-researched civilian criminal investigations. Differing from civilian police detectives, most military investigators–as disciplinary supervisors and military police personnel–have a number of tasks to accomplish, which include leading in combat and ensuring military readiness. Military investigations can lead to substantive negative or positive consequences for military readiness, including mental health, unit cohesion and subjective legal certainty. This impact on unit cohesion and mental health is influenced by any prior history of distress or trauma; military investigations are often preceded by contravention of internal disciplinary acts, complaints and traumatic events. This study explores factors in the differing military and legal systems of Germany and the United Kingdom (UK) that might help military personnel to successfully conduct investigations while ensuring deployment readiness and maintaining human rights.