Flags are among the most ubiquitous popular images today. That was also true for the late medieval and early modern eras during which flags played crucial roles in articulating personal, communal, and proto-national identities. Yet because of a tainted association with Nazi scholarship as well as pedantic cataloguing processes of vexillological study, flags have escaped sustained art historical analysis in spite of their omnipresence. This paper proposes to reinsert flags into the art historical purview. Through the example of the deployment of captured flags from the Battle of Sempach (1386) and the Burgundian Wars (1476–1477) in the Swiss city of Lucerne, I explore how these objects functioned as potent images in the writing of Lucerne’s history. Because silk flags are inherently fragile, their afterlives were assured through practices of copying. These chains of substitutes were mobilized to create different historical narratives depending on the context of their deployment. Tracking how the same images (but different objects) developed over time allows us to think through the paradoxes of these popular objects: flags are fragile but enduring, as well as potent but risky and unstable. Although their appearances are codified and hence seemingly fixed, their meanings can shift. In part because they are “popularly” known by a broad audience, these shifts play themselves out in a sometimes hotly debated public arena. In the context of Lucerne, captured flags traversed various locations and media (from the battlefield, to churches, to secular spaces, to commemorative festivals, to postcards). These uses of flags attempted to tame historical and political instability through the creation of popular imagery that purported to stabilize different political agendas. They thereby contributed as dynamic agents to the production of historical knowledge. Recapturing the contingencies of these objects of visual and material culture allows us to think through the ways in which seemingly fixed popular images like flags are in fact surprisingly unruly.