After a few years his military career reactivated and by 1805 he was already major-general. He participated in the campaigns from 1806 to 1807 in East Prussia against France and 1810 in part of Turkey. He accompanied his father Eugen, who was commander of Prussian Reserve, in 1806. He joined staff of Russian General Bennigsen. In 1812, he was a division commander (4th div of II Corps) under Barclay de Tolly. During the French invasion of Russia he fought at the Battles of Borodino and Krasnoi. At the War of the Sixth Coalition he fought in five major battles. In the battle of Lutzen, Eugen's corps was heavily engaged and suffered many casualties recapturing villages from the French. In the battle of Bautzen, Eugen's men, acting as the Russian rearguard, slowed the French advance by defending positions on hills and behind a village. The slow advance of the French infuriated Napoleon himself, who took over the command of the advance guard personally-but he did no better. In the battle of Dresden, the heavily outnumbered Eugen held off the forces of the French general Vandamme for a day before retreating. In the battle of Kulm, Eugen suffered over 3,000 casualties in his victorious rematch with Vandamme. And in the battle of Leipzig, most of Eugen's artillery was destroyed by the French. Despite this, and despite the losses at Kulm only a few weeks before, Eugen's infantry made a heroic, tenacious stand. Two-thirds of his troops and all of his regimental commanders became casualties.