War Games Gone Wrong?

This article is very interesting and gives us a good glimpse of what went wrong on 9/11.

So many war games were being run on 9/11 or had been run just before 9/11, that ATC and NORAD were totally confused and didn't mount the normal response to hijackings.

This can certainly explain some things, but not all. For instance-- were the hijackings real or part of the war-game?