Historians have increasingly stressed the impact of the French Revolutionary and Napoleonic Wars on Britain and Ireland. Less attention, however, has been paid to the legacies of martial mobilization after 1815. Drawing on hitherto unused press and archival sources, this article assesses the implications of wartime military expansion for the music profession, and musical culture more generally, in the decades after Waterloo. It demonstrates that men and boys who honed their instrumental skills in uniform embarked on a variety of civilian musical careers, becoming instructors, wind performers, composers, and even opera singers. The article traces the post-war circulation of regimental instruments and reveals that a multitude of militia and volunteer bands remained active long after demobilization. The wartime proliferation of military bands, moreover, encouraged the subsequent spread of quasi-martial wind ensembles in wider society. Finally, the article proves that brass bands were first introduced to Britain and Ireland in a regimental guise. The influence of the military on musical culture after 1815, in short, was palpable and often profound, and manifested itself in numerous ways and settings.