A secondary Prussian force under General Johann Dietrich von Hülsen repulsed an Austrian advance into Saxony on 20 August in the Battle of Strehla. The Prussians and Austrians spent September skirmishing and manoeuvring in Silesia, while Saltykov's Russians held back in western Poland. With Prussian forces concentrated in Silesia and Saxony, Brandenburg was left largely undefended. In early October a Russian corps under General Gottlob Heinrich Tottleben advanced through Neumark and joined Lacy's Austrians in briefly occupying Berlin, where they demanded ransoms, seized arsenals and freed prisoners of war. However, the Russians soon pulled back to Frankfurt an der Oder for want of supplies, while Lacy's force moved south to support Daun as he sought a decisive engagement with Frederick in Saxony.