He was succeeded by his son, Frederick William III (1797–1840), who involved Prussia in the disastrous Fourth Coalition. The Prussian Army was decisively defeated in the battles of Saalfeld, Jena, and Auerstedt in 1806. The Prussians' famed discipline collapsed and led to widescale surrendering among infantry, cavalry, and garrisons. While some Prussian commanders acquitted themselves well, such as L'Estocq at Eylau, Gneisenau at Kolberg, and Blücher at Lübeck, they were not enough to reverse Jena-Auerstedt. Prussia submitted to major territorial losses, a standing army of only 42,000 men, and an alliance with France in the Treaty of Tilsit (1807).