Excellent summary of the book. I look forward to reading it.
The British sending in the Black Watch to replace the Marines south of Baghdad represents only one battalion. If the ability to launch the offensive depended on the arrival of one battalion - and there was not one more U.S. battalion available in the Army or Marines - it represents ammunition for the McCain/Kerry thesis that we didn't have enough troops in Iraq.
I read it already. The Marines asked specifically for the Black Watch, there were other troops available. They also asked for a specific Army unit - the same unit also. This is unusual, but not unheard of. McCain was and is full of himself. The ability to mount the op was in no way limited by available troops. You have to understand Fallujah in relation to Hue City where the Marines were the defender, not the attacker. The Marines know their history. They knew it was going to be nasty, and asked for the the best to go in with them.