In any significant engagement you're going to have a long period where you consistently fuck up and have to adjust. A healthy organization actually will adjust, though, and that's more important, because whether you get it right at first has more to do with whether you've been doing substantially the same thing recently, which for the military largely depends upon how warlike the politicians have been lately ;)
Bingo: the US military or at least the Army has long had the reputation of starting out the greenest and learning the fastest.
What struck me the most WRT Vietnam was the learning part horribly broke down, at least in the Army (I actually haven't studied much about the Marines there).
One reason blue water navies tend to do better right off the bat in a war is that just doing the blue water navy thing (keeping your ships from colliding and sinking when they're out at sea per the doctrine) requires a minimal level of competence that just isn't required in ground force exercises (assuming you can get the money to do any of any scale).
Hmmm, gunnery exercises probably also work better. On the other hand, every major naval force at the beginning of WWII had major flaws with their torpedoes ... and the US Navy was pretty much the worst in dealing with them (Washington refused to listen and the various flaws had to be debugged in Hawaii; by contrast the Germans found and fixed theirs quickly and cashiered two officers responsible for them (the latter from memory)).
