To help the British armed forces minimise mental health problems while undertaking military duties, operational psychological support is provided by military mental health nurses. This series of two articles is part of the first qualitative research completed in Afghanistan by British armed forces into the effectiveness of the military mental health nursing role. The authors aim to increase understanding of the factors that affect the delivery of nursing care during an operational deployment, including educational and clinical competency, multiprofessional and multinational boundaries, and the challenges of providing nursing care for both military personnel and local nationals. This article, the first of the two-part series, looks at the set up of the study, while the second article (featured in the next issue of JCN) will look at the study findings.