How (and why) did Hitler create “the world's largest traffic jam?”

How (and why) did Hitler create “the world's largest traffic jam?”

This is not a reference to "current events" but to Fall Blau the 1942 attack on the southern Soviet Union by Army Group South. The campaign started smoothly enough, with the approach to (and capture of Vornezh) by Herman Hoth's 4th Panzer Army. Then Paulus' Sixth Army followed with an advance in the Don bend. So far so good.

The two armies mentioned were later grouped into Army Group B. At the extreme south, Army Group A captured Rostov-on-the Don, crossed the river, headed south for the Maikop oil fields, and found its way blocked, not by the Soviets, but by Hoth's 4th Panzer army, which had been ordered by Hitler to support the thrust to the Caucasus. Moreover, Hoth's troops would not yield the right of way to Army Group A, creating a massive snarl at a time when fuel was a scarce commodity.

How did this come about? Even if Hitler wanted Hoth (and the 4th Roumanian army) to support Army Group A, why didn't he subordinate Hoth to Army Group A instead of letting him operate independently? And why would Hoth be allowed move in the same direction, south, and ultimately over the same roads as Army Group A instead of e.g. "east then south," like the 4th Roumanian Army? (This would have put Hoth parallel to Army Group A, protecting its weak flank and would have created a broader front that would have improved the Germans' chances of success.)

(Note: I am not asking why Hitler attacked in the south or why he sent Hoth's army to support Army Group A. The question is why was the tactical execution of his directives so poor, resulting in a major duplication of effort.)

Because Hitler was a horrible "traffic cop."

One version of Fall Blau called for the Germans to advance east to Stalingrad, then along a broad front south on a line from that city, and Rostov on the Don. While Army Group South would have been advancing into "two" directions, it would have been one at a time, rather than two different directions.

Hitler wrongly believed that the "cork in the bottle" was Rostov on the Don. So he diverted part of Army Group B (Hoth's Fourth Panzer Army), to help Army Group A (under Kleist) to capture this key city. In fact, Kleist did not need this help (and Hoth's Panzer were actually in the way), as evidenced by the fact that Kleist advanced 300 miles to Maikop in about a month. Where Kleist needed help was further east, toward Grozny, and Hoth could have provided this leverage by moving south parallel to Kleist, on the east.

In effect, Hitler's view became self-fulfilling as he created a bottleneck at Rostov, and wasted a month of campaigning from Hoth that might have made the difference around Stalingrad. Subsequent events showed that the narrow corridor through Rostov was insufficient to supply both Kleist and Hoth, whereas the subsequent campaign showed that it was (barely) possible to supply both Hoth and Kleist if Hoth's starting point was Stalingrad.

Additional Source: Gordon Corrigan, "The Second World War: A Military History."