This chapter examines Austria at its post-Napoleonic peak, assessing congress diplomacy and the pecuniary, forts-based system that undergirded it. The Habsburg Monarchy emerged from the Napoleonic Wars in a position of unprecedented strength. In the postwar settlement at the Congress of Vienna, Austria regained lost territories to form an expanded empire whose possessions and dependencies stretched from Venice to Cracow. To protect these enlarged holdings, Habsburg leaders extrapolated on past frontier strategies to build a European-wide security system based on two broad components: a reorganized and fortified network of buffer territories integrating neighboring lands into Austrian defense; and elaborate diplomatic structures that mediated conflict and co-opted rivals into the joint management of Habsburg buffers. The resulting “Vienna system” mitigated the time pressure of managing multiple frontiers while converting long-standing enemies into participants in the maintenance of Austrian power. This, in turn, obviated the need for large standing military commitments on the scale that would have been demanded to manage Austria’s sprawling position through force alone. The apogee of Habsburg strategic statecraft, this system of security endowed Austria with many of the attributes of hegemony at an affordable cost to itself, while creating conditions of European stability that lasted for half a century.