The Germans fought and lost the Battle of Kursk to the Russians, and from then on, it was pretty much a nonstop retreat for the Germans (except for the Siege of Warsaw Poland) all the way to the Reistag in Berlin, Germany.
Kursk is located in western Russia. Battle fought on July 5 – Aug. 23, 1943 Check for location on MapQuest.com. http://www.mapquest.com/maps/map.adp?formtype=address&country=RU&addtohistory=&city=kursk
The biggest tank battle of WWII was the Battle of Kursk (5jul-23aug1943) fought between Russian and German tanks at Kursk in western Russia, on the Seym River Over 6000 tanks, 2 million troops, and 4000 aircraft took part in this one battle.