Yorck von Wartenburg or York von Wartenburg, Ludwig, Graf (both: lŏtˈvĭkh gräf yôrk fən värˈtənbŏrkh) [key], 1759–1830, Prussian army officer. He commanded the Prussian auxiliary corps that had been sent to aid in the campaign of the French emperor Napoleon I against Russia (1812). When he realized that the expedition was doomed to failure he withdrew on his own responsibility from the fighting and concluded the Convention of Tauroggen with the Russians (see Taurage). His action was lauded by the nationalistic Prussians, desirous of escaping from their virtual vassalage to France, which had been imposed by the treaty of Tilsit in 1807 following Prussia's defeat by France. King Frederick William III of Prussia subsequently approved his act, and Prussia entered the coalition against Napoleon. Yorck defeated (1813) a French force at Wartenburg in Saxony, thus earning his title.