In April 1759 Frederick led his main army from Saxony into Lower Silesia to keep the Russian army in western Poland separated from Daun's Austrians in Bohemia. Meanwhile, a smaller Prussian force under Frederick's younger brother, Prince Henry, remained in Saxony to harass Bohemia through the Ore Mountains, winning the Battle of Peterswalde and a series of other minor engagements, as well as destroying several Austrian ammunition dumps and bridges before retreating into Saxony. The Russians continued to press into Neumark; on 23 July the new Russian commander, Count Pyotr Saltykov, led 47,000 men in defeating 26,000 Prussians commanded by General Carl Heinrich von Wedel at the Battle of Kay. The Russians advanced westward toward the Oder, while Frederick led reinforcements northward to join Wedel and face Saltykov, leaving Prince Henry and General Heinrich August de la Motte Fouqué to see to the defence of Saxony and Silesia, respectively.