The war planners - they were thinking of bringing the troop number to 30,000 two months after "mission accomplished"
First of all (not that I necessarily doubt you), which "war planners"? "The"? All of them? Do you have a link?
Second: "thinking of"? Ok, well, I was thinking of winning the lottery. Didn't happen. Big deal. When it transpired that I didn't win the lottery, I made life decisions accordingly. When it transpired that it didn't make sense to reduce the troop # to 30000 (if indeed "the" war planners ever seriously entertained such an idea), they didn't.
The point?
All grownups should understand that this is what war is, you know, like. The nature of war is such that there is an enemy working against your wishes. This idea that you can "calculate" (by computer?) precisely what should be done, and get the "right answers", and then the war goes perfectly - the only word that comes to mind is, infantile.