Following the German success with their Gorlice–Tarnów offensive, Hans von Seeckt proposed that August von Mackensen's Eleventh Army should advance north towards Brest-Litovsk, with their flanks shielded by the rivers Vistula and Bug. Mackensen and Erich von Falkenhayn supported this strategy of attacking the Russian salient in Poland, and forcing a decisive battle. "Ober Ost", led by Paul von Hindenberg and Erich Ludendorff, would attack towards the southeast, while Mackensen turned north, and the Austro-Hungarian Second Army attacked east. The "Ober Ost" Twelfth Army, led by Max von Gallwitz, would advance to the northeast of Warsaw, while the Ninth Army, led by Prince Leopold of Bavaria, the Woyrsch Corps, led by Remus von Woyrsch, and the Austro-Hungarian First Army, led by Paul Puhallo von Brlog, pushed the Russians eastward to the Vistula. The Army of the Bug, led by Alexander von Linsingen, the Austro-Hungarian Second and Seventh Armies, led by Eduard von Böhm-Ermolli and Karl von Pflanzer-Baltin respectively, protected Mackensen's eastern flank. On Mackensen's western flank was the Austro-Hungarian Fourth Army, led by Archduke Joseph Ferdinand.