The "Operation Braunschweig", from July 23, 1942 is preponderant in the German failure. While it was planned during "Blau" that a strong group comprising the 6th Army and especially the 4th Panzer Army, covered on the Don by the ARMIR (Armata Italiana in Russia), the Hungarians and the Romanians, plus the 2nd Armed near Voronezh were to rush into the great loop of the Don and the Don-Volga corridor, the "Braunschweig" operation routed the 4th Panzer Army (in fact the XXXXVIII. Reinforced Panzer Corps) towards the Caucasus, leaving the 6th Army alone (also reinforced) the task of conquering the great loop of the Don and Stalingrad.
This change has two disastrous consequences:
1. the 6th Army is no longer strong enough to operate alone, decisively, in the great bend of the Don. This implies a stiffening of Soviet resistance in the face of the weakening of the German assault forces in the sector, thus a slowing of the progression towards Stalingrad detrimental to its rapid conquest.
2. the 4th Panzer Army, by joining the 1st Panzer Army and the 17th Army in their progress towards the Caucasus, causes an unexpected and catastrophic effect:it completely jams the logistical routes of Heeresgruppe A and also slows down the progress, without even being able to enter into line!
Thus, in mid-August 1942, the 4th Panzer Army was reoriented to the northeast, towards Stalingrad. Three weeks have thus been lost without noticeable gain on the Caucasus front and with negative effects in the great loop of the Don.