[But then again Luttwak was the guy that said that Gulf War I was going to be a bloodbath for the Allied forces.]
He was merely repeating what military officials had determined to be the worst case scenario. IIRC, 30,000 body bags had been readied for friendly casualties. Prior large-scale conventional battles had been bloody, dating back to WWII. Heck, even in the Korean War, the US lost 38,000 troops in 3 years of fighting, a light toll compared to any similar period of WWII.