During the initial period of formation, Janissaries were expert archers, but they began adopting firearms as soon as such became available during the 1440s. The siege of Vienna in 1529 confirmed the reputation of their engineers, e.g. sappers and miners. In melee combat they used axes and kilijs. Originally in peacetime they could carry only clubs or daggers, unless they served as border troops. Turkish yatagan swords were the signature weapon of the Janissaries, almost a symbol of the corps. Janissaries who guarded the palace (Zülüflü Baltacılar) carried long-shafted axes and halberds.