PS: I checked Pogue’s “Supreme Command.” He does not mention Ike’s conference with Devers at all. The only mention of 6th Army Group is its surprising advance to Strasbourg. Then it skips to Ike’s orders to have 7th Army support Patton’s Dec. 19 Saar offensive. No mention about how that decision came about.
I stumbled upon Ike Library and the was quite a few documents about his correspondence with Devers during the war. The links only took you to a very thin reading of what was contained. I didn’t have time to explore how to actually get the documents.
Devers was artillery. He was one of the men who modernized fire control at Ft. Sill, which paved the way for the devastating effectiveness of American artillery in WWII.
I can't figure out what the problem was leading to the Ike personality dispute. During the North Africa and Sicily campaigns, Devers replaced Ike as commander of the ETO, which at that time was just the British Isles. Maybe Ike thought he was trying to steal his command?
Marshall really liked Devers, so it seems a little odd that Ike took such a dislike to him.