One of the things I noted in Eisenhower's Lieutenants was how often and how quickly commanders at different levels were relieved by the bosses. Turns out that's gone away almost entirely over the decades since World War 2, and Ricks feels that isn't to the benefit of the Army.
One key thing Ricks points out is that as used by Marshall and Eisenhower, relief didn't necessarily mean an officer's career was over. In many cases, unless the officer seemed too old, inflexible, or otherwise incapable of adapting, he would be given another chance to command later. Nowadays, to be relieved is seen as being the end of the line. One colonel Ricks quotes says you might as well court-martial an officer.
What emerges in The Generals is the numerous changes that have taken place in how command is viewed. In World War 2, commanders were expected to be aggressive (within reason), to get results, but in many cases, how they achieved those results was up to them. They were allowed - encouraged, really - to adapt their approach, and show initiative. If they did and it worked, they'd likely be promoted, to see how they handled greater responsibility. If they tried and failed, they'd get another chance. If they failed to show aggression, adaptability, initiative, and cooperative spirit, they were likely done.
Since then, there's been a shift to where commanders are not meant to show initiative, and are supposed to carry out operations as ordered by their superiors. Being a team player means everyone does things the same way, and no one is supposed to stand out. Trying something risky and new had better work, because if you buck the accepted way of doing things and fail, you're probably done. Being mediocre in the approved manner will still be rewarded. What's more, the higher officers, the generals, aren't thinking on the proper level. Ricks argues generals need to be thinking about why they're waging this war, and what they're hoping to accomplish, leaving the manner of how to win battles to the subordinates on the ground. Instead, the generals have decided those sorts of concerns are the politicians' worry, and they focus on tactics, which turns them into micromanagers with no conception of the larger picture.
One thing I wasn't totally clear on was why the Army sort of closed ranks. It starts a bit in Korea, but accelerates in subsequent conflicts where the Army adopts an "us vs. them" approach, where "them" refers to American politicians, media, and the public. Which is perhaps one of the reasons relief goes out of fashion. If you remove a subordinate, it looks like an admission of failure, that you either aren't doing things right on the battlefield, or aren't doing things right in training your officers. The Army seems increasingly sensitive to outside criticism, so they takes steps to minimize it, which creates a culture where people aren't held accountable for their mistakes and unethical (or criminal) actions, which, once word of that leaks, produces more external criticism, which makes them close ranks all the more. My best guess is that Korea and especially Vietnam were not popular wars with the public, and the military took a lot of the brunt of the blame, and they felt that was unfair, they had been ordered to fight by the government, and that helped produce the more adversarial relationship (especially between military command and the government, which doesn't help).
One other thing. In Roosevelt's Centurions, Persico mentions Churchill consistently delaying the Allies invading France from across the Channel, citing among other things, the need for American troops to gain combat experience (and officers battlefield command experience) before they faced the Wehrmacht. Persico didn't buy it, pointing out that on D-Day, 60% of the American troops had still never seen combat, and that Churchill was really more concerned with securing the Mediterranean to help the British maintain their grip on their Empire (figuring FDR wasn't serious about wanting them to grant their imperial possessions self-determination after the war). Ricks, on the other hand, agrees with Churchill, both on the need for combat experience argument, but also the idea the operations in North Africa, Italy, and Sicily diverted German troops away from the Channel. Persico would no doubt counter it also diverted Allied troops away from the Normandy landing. I'm not sure who's right, I just found the disagreement interesting.
'By the time the war ended, in 1953, the Marshall approach to generalship had severely eroded. This was in part because removing senior officers in a small, unpopular war proved politically difficult. A wave of high-level reliefs early in the war provoked fear at the top of the Army that more such actions would lead Congress to ask uncomfortable questions. One must wonder about a system that seemingly was willing to accept the disastrous consequences of leaving unfit generals in command of American troops in order to avoid difficult inquiries from members of Congress.'