I can see the strategic value of Stalingrad as it was the biggest port and industrial city on the Volga.
Stalin seemed every bit as determined to defend the city as Hitler was determined to take the city and that’s what lead to the biggest and bloodiest battle in recorded human history.
The most perplexing aspect of the battle was Hitler’s stubborn refusal to authorize a breakout from the pocket while the 6th Army was still viable. ALL of his generals advised a breakout. Only RM Goering, perhaps his judgment impaired by his addiction to morphine, suggested the 6th Army could be supplied by an airlift-—pure insanity given the atrocious weather conditions. And Hitler himself by now given a daily injection of a cocktail of drugs supplied by his quack physician. Hitler’s lack of military logic probably is the reason he never rose higher than corporal when he served in the army.
Hitler liked to look at maps and pretend he was a genius to make decisions. Real generals look at logistics, from both sides, before they make decisions. Looking at how well the German Army did during WWII with a total idiot like Hitler calling the shots is amazing. That the German army didn't kill the SOB for wasting their army is even more amazing.
Going back to the topic of the thread, Sherman (and Grant) understood logistics. Sherman saw that he could march through the South 'living off the land' while at the same time depriving his enemy of the resources of that same land.
In WWII, it was bombing raids on factories and transportation centers. That is logistics. It's ugly, but that is how it works and why war should be avoided.
Certainly refusing to allow the 6th Army to break out of the Stalingrad pocket was colossally stupid. That was in keeping with the way Hitler thought war should be fought. He had no conception of the value of a strategic retreat. He always was pushing his forces forward, or failing the ability to move forward, at least die holding every inch of ground already taken. The refusal to retreat from Stalingrad is quite in keeping with that notion of warfare. The fact that Goering told Hitler that the army could be supplied was just confirmation to Hitler that retreat should not be an option. Hitler wanted to believe Goering so there was no way he would have even considered that the idea was completely unrealistic.
Having said that, your point about Stalingrad’s strategic value is taken, but nonetheless taking Stalingrad was NOT the primary goal of the campaign. The primary goal of the campaign was control of the Caucus oil fields. That objective would have been far more valuable than Stalingrad. The Germans could have bypassed Stalingrad and drove toward the Caucus, thereby preserving a significant amount of their fighting ability. Going after Stalingrad was not as colossal a blunder as refusing to break out of the pocket there, but it was nonetheless a mistake.