How many groups did von Rundstedt command ?
After Uman Budyonny 's forces massed around Kiev – over 700,000 men – were left dangerously exposed , with Kleist 's 1 st Panzer Army regrouping to the south - east and General Heinz Guderian 's 2nd Panzer Army ( part of Army Group Centre ) smashing General Yeromenko 's Briansk Front and advancing south from Gomel in White Russia , on a line well east of Kiev .