 Complete the following phrase:  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 Saltykovs 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 Lacys Austrians in briefly 