Military exercises are rarely straightforward in either intention or outcome. Official policy and governance about exercises have not kept up with the complexity of the current national and international contexts. In addition to collective training, exercises are now used for a wide variety of purposes, such as fostering alliance cohesion and defence diplomacy. In this article, Beatrice Heuser and Harold Simpson argue that the diverse effects and outcomes of exercises merit further investigation, and future guidance for British practitioners will reflect this.