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Introduction It has been suggested that military populations undergoing arduous training are more susceptible to respiratory tract infection (RTI), and it has been postulated that this may be due to impaired immune function.Methods A narrative literature review was conducted addressing the risk of respiratory infection and host immune function changes during arduous military training, screening published articles (1980–2025) against a framework developed from expert consensus by Simpson et al on research needs for exercise immunology, adapted for military-specific variables and confounders.Results 22 studies, comprising 842 participants (656 male, 74 female and 112 unclear) were included, identifying marked disparity across studies for physical and non-physical training stressors, sampling timing and selection of immune readouts. 12/22 (54.5%) measured deviations from baseline, while 9/22 (40.9%) studies included an internal intervention/comparator group (seven nutritional, one exercise and one sleep deprivation). 8/22 (36.4%) studies reported on RTI symptoms, half (4/8) found an increased risk but none used confirmatory respiratory diagnostics. In terms of immune markers, key findings included lymphopenia and a rising plasma IL-6 in the first few days of training and reduced blood T-cell ex vivo proliferative responses during two 6-week training periods.Conclusions Arduous military training may be associated with an increased susceptibility to RTI symptoms but the absence of microbiological data limits interpretation. The clinical relevance of observed changes in immune readouts remains unclear, and no single assay emerged as an optimal marker of ‘risk’. Military populations conducting arduous training represent a distinct population with unique physical and psychological demands that necessitate further representative research.