The stressors associated with emergency medical teams responding to critical incidents are well documented; however, the impact of such duties on the UK military personnel had never been investigated. This study explored the psychosocial effects of Medical Emergency Response Teams (MERT) operating in Afghanistan to inform the development of a Resilience Model. A structured and contextually relevant process could then be applied for a team's preparation for, delivery of and recovery from, their duties. A qualitative cross-sectional design used semi-structured interviews and 15 multidisciplinary team members participated. Interviews were transcribed verbatim and data were systematically analysed using grounded theory. Emergent theory poses that developing resilience against the demands of this role is dependent upon personnel having a realistic understanding of the deployed environment by phased immersion within it. This preparatory training generates situational awareness, trust and strong team cohesion, which together with peer and organizational support are necessary factors to effectively cope with the role. To limit the costs of caring, there is a need for MERT personnel to segregate the physiological and emotional aspects of delivering care to the injured; those unable to do so may be at greater risk of poor mental health outcomes. The preparatory training of MERT personnel must be further developed to provide an immersive environment that more closely matches the reality of the role. A period of stability is required post deployment with the support of peers to enable personnel to more efficiently transition back to their home life. © 2020 Crown copyright. Stress and Health © 2020 John Wiley & Sons Ltd.