By this point Frederick was increasingly concerned by the Russian advance from the east and marched to counter it. Just east of the Oder in Brandenburg-Neumark, at the Battle of Zorndorf (now Sarbinowo, Poland), a Prussian army of 35,000 men under Frederick on Aug. 25, 1758, fought a Russian army of 43,000 commanded by Count William Fermor. Both sides suffered heavy casualties the Prussians 12,800, the Russians 18,000 but the Russians withdrew, and Frederick claimed victory. In the undecided Battle of Tornow on 25 September, a Swedish army repulsed six assaults by a Prussian army but did not push on Berlin following the Battle of Fehrbellin.

Answer this question, if possible (if impossible, reply "unanswerable"): How large a force did Frederick send against the occupying Russians?
35,000 men