Prussian control of Silesia was confirmed in the Treaty of Hubertusburg (1763). Severe casualties had led the king to admit middle class officers during the war, but this trend was reversed afterwards. The offensive-minded Frederick advocated the oblique order of battle, which required considerable discipline and mobility. This tactic failed at Kunersdorf largely because of the terrain, which could not be used to an advantage, and because the Russians had arrived early and fortified themselves on the high ground. Frederick used oblique order to great success at Hohenfriedberg and later Leuthen. After a few initial salvos, the infantry was to advance quickly for a bayonet charge. The Prussian cavalry was to attack as a large formation with swords before the opposing cavalry could attack. The first garrison began construction in Berlin in 1764. While Frederick William I wanted to have a mostly native-born army, Frederick II wanted to have a mostly foreign-born army, preferring to have native Prussians be taxpayers and producers. The Prussian Army consisted of 187,000 soldiers in 1776, 90,000 of whom were Prussian subjects in central and eastern Prussia. The remainder were foreign (both German and non-German) volunteers or conscripts. Frederick established the "Gardes du Corps" as the royal guard. Many troops were disloyal, such as mercenaries or those acquired through impressment, while troops recruited from the canton system displayed strong regional, and nascent national, pride. During the Seven Years' War, the elite regiments of the army were almost entirely composed of native Prussians. By the end of Frederick's reign, the army had become an integral part of Prussian society and numbered 200,000 soldiers, making it the third largest in Europe after the armies of Russia and Austria. The social classes were all expected to serve the state and its army — the nobility led the army, the middle class supplied the army, and the peasants composed the army. Minister Friedrich von Schrötter remarked that, "Prussia was not a country with an army, but an army with a country". Frederick the Great's successor, his nephew Frederick William II (1786–97), relaxed conditions in Prussia and had little interest in war. He delegated responsibility to the aged Charles William Ferdinand, Duke of Brunswick, and the army began to degrade in quality. Led by veterans of the Silesian Wars, the Prussian Army was ill-equipped to deal with Revolutionary France.