In October 1657, the Swedish army stormed the Danish fortress Frederiksodde, forcing its defenders to surrender their colours and guidons. This dramatic event started a process whereby the flags, as trophies of war, were heritagised. In the seventeenth century, captured flags were delivered from the battlefields of Europe to the Great Armoury in Stockholm. Here, in one of the earliest museums in Sweden, they were exhibited in a historicised display modelled on European ideals. As more Romantic sensitivities towards history evolved, the collection was called upon to serve a new national narrative. Captured Colours investigates the agency of military flags in Early Modern Swedish heritage production. By following the group of Danish flags captured in 1657 from the time of their production until 1817, this study brings to light an assemblage of people, objects and practices that constituted military flags as important agents in Early Modern displays of power. Drawing on military treatises, archival sources, visual representations, and the preserved flags, it explores how flags became the “sacred objects” of the army. It investigates how they were heritagised through display and documentation, offering new insights into the history of Swedish museums. This is a doctoral thesis in Art History at Stockholm University, Sweden 2025