(August 2630, 1914) Battle in World War I between Germany and Russia in modern northeastern Poland.
Two Russian armies invaded German East Prussia but became separated. German forces under Paul von Hindenburg attacked one of the isolated armies and forced its retreat, inflicting Russian casualties of over 30,000 and capturing over 90,000 men. German casualties were about 13,000. The battle was disastrous for Russia, but it forced Germany to divert troops from the attack on France.