Unlike ancient Roman emperors who could call upon absolute power, the rulers of the mostly German "Holy Roman Empire" (which also had Polish, Hungarian and Bohemian emperors as well) weren't always "born in the purple" so to speak, but were often chosen via semi-democratic (or rather, oligarchical) means through election by a council of nobles and clergy, the former often being their own peers invested by the Pope to elect an Emperor. For this reason and the fact that no centralisation really existed in matters of administration, finance nor military control, mediaeval Emperors were often forced to fall back on the strength of their own feudal possessions, and were also forced to rely on the swords of their most loyal men for security and victory.