Emergency medical care for seriously injured patients in war or warlike situations is highly important when it comes to soldiers’ survival and morale. The Swedish Armed Forces sends nurses, who have limited experience of caring for injured personnel in the field, on a variety of international missions. The aim of this investigation was to identify the kind of criteria nurses rely on when assessing acute trauma and what factors are affecting the emergency care of injured soldiers. A phenomenographic research approach based on interviews was used. The database for the study consists of twelve nurses who served in Bosnia in 1994–1996. The criteria nurses rely on, when assessing acute trauma in emergency care, could be described in terms of domain-specific criteria such as a physiological, an anatomical, a causal and a holistic approach as well as contextual criteria such as being able to communicate, having a sense of belonging, the military environment, the conscript medical orderly and familiarity with health-caring activity. The present study shows that the specific contextual factors affecting emergency care in the field must also be practised before the nurse faces military emergency care situations. This calls for realistic exercises and training programs, where experience from civilian emergency care is interwoven with the knowledge specific to military medical care.