When the U.S. Amy 1st Cavalry division was in Iraq recently, it found itself in charge of 52 battalions of combat and support troops. This is more than twice as many as a division usually handles, and was only possible because of improvements in communications, and the skill of staff and communications personnel in getting hardware and software reconfigured to cope with all the information coming from, and going to, all those battalions. Without intending to be, this was a real life test of the future force the army is currently working on. Better communications are supposed to mean headquarters can be smaller, and do more work. As is typical of wartime situation, troops end up doing what was, in peacetime, believed impossible, or at least very difficult.
American combat divisions have, since World War II, typically had a few additional battalions attached. But sometimes, the division had to control half a dozen or more additional battalions, and it wasnt easy. It wasnt until the Internet came along that there was a communications system that was, inadvertently, designed to enable a division headquarters to handle a much larger number of units. Its all about email, message boards, user friendly databases and instant messaging. Makes a big difference. Made a crucial difference. Division commanders, usually Major Generals, can now do the work of Corps Commanders (usually Lieutenant Generals.) As a result, the Corps Headquarters may disappear as unneeded.