At first the Alpini were organized as a militia, capable of defending Italy's northern mountainous borders. Austria's surrender in the Austro-Prussian War of 1866 resulted in Italy annexing the province of Venetia, the northern borders of which coincided in large part with the Alpine Arch. Prior to gaining the new northern borders, homeland defence was based on the so-called Quadrilatero strategy. That outdated strategy, however, ignored the geopolitics of the new Italian Kingdom. It called for primary defence of the Po Valley region (Pianura Padana) farther to the southwest, but left the Alpine region undefended (as it was considered a territory mainly unsuitable for military operations).