A major problem of state and institution building in Yugoslavia after 1918 was that the end of the war was not a complete caesura between separate South Slav pasts and a unified ‘Yugoslav’ future: much historical and institutional baggage was carried over into the new state. This was obviously the case with the Yugoslav army, where creating a new institution entirely from scratch was impossible, given the immediate internal and external threats that faced the new state and given the prestige and the military efficacy of the Serbian army. The Yugoslav army was consciously modelled on the pre-war Serbian army, not only in terms of its institutional framework, but also in terms of its ethos and ideology. There was little space in this ideology for commemorating Austria–Hungary’s war, just as there was little space in the Czechoslovak, Polish or Romanian armies. It was difficult to fuse Austro-Hungarian and Serbian veterans into one army, and problems were especially acute in the officer corps. This article addresses some of the successes and failures encountered in the attempt to fuse disparate and often antithetical military institutional cultures in Yugoslavia in the decade after the end of the First World War.