We did so with far fewer than he suggested was needed. What we didn't do was to 1)attack from the north and grind up the northern nutballs, 2) significantly increase the size of the standing military to account for rotations, and 3) keep Iran out of it...which was largely a matter of poorly dealing with Democrats and the State Department.
Those that said we needed more troops in the initial invasion were shown quite clearly to be wrong...and we still aren't to their expected casualty levels.
I'll grant you that his numbers may have needed some work, but he was still right--we needed more people to get it done. Rumsfeld and GEN Franks disagreed. The invasion absolutely worked beautifully, but the human terrain was far more complex than Afghanistan, something that was obviously underestimated.
Would casualties have been a lot lower had we put 200,000-300,000 Soldiers/Marines into Iraq? I have no idea, but I'd be surprised if the overall pacification process had taken this long.
1)attack from the north and grind up the northern nutballs
We can thank our Turkish "friends" there; nothing we can do about that short of invading them, too
2) significantly increase the size of the standing military to account for rotations
Short of initiating a draft, this is a very long term solution, and for anything resembling a near-term solution, unworkable.
3) keep Iran out of it...which was largely a matter of poorly dealing with Democrats and the State Department.
Iran has much bigger allies than the Democrats or a useless State Dept. They have the 60%+ Shi'ite population in Iraq and a starved-for-attention Moqtada al Sadr and his personal army. We got so wrapped around the axle with AQI that the Mahdi Army practically got a pass by default. Now those b*st*rds are getting what they deserve. There's a special place in hell for every one of 'em.