The initial advance of the 6th Army was so successful that Hitler intervened and ordered the 4th Panzer Army to join Army Group South (A) to the south. A massive traffic jam resulted when the 4th Panzer and the 1st Panzer choked the roads, stopping both dead while they cleared the mess of thousands of vehicles. The delay is thought to have delayed the advance at least one week. With the advance now slowed, Hitler changed his mind and reassigned the 4th Panzer Army back to the attack on Stalingrad.