How would zombies overwhelm a tank division!?!?!?! Tanks would just run them over....
Yes, he wrote a section of the book on a Battle known as "The Battle of Yonkers", which is right outside of New York City.
Actually, I really don't know why they didn't just run them over, but apparently, the U.S. Army, in their infinite wisdom, had set up a World War 1 shooting gallery so to say. One soldier said, and I paraphrase, "Instead of putting a rifle squad on the 30th floor of that office building, they had us dig a trench and set up barbwires and sand bags and then lined us up to face the Zombie horde". So, basically, the U.S. Army wanted a propaganda reel to be made out of that battle. So, with those Infantrymen on the ground, lined up, they stationed their AFVs behind the Infantry and laid down fire. Unfortunately, the biggest problem was ammo supply, and because M1A2 Abrams carry APFSDS rounds the majority of the time, were nearly useless against the 7 million zombie horde that hit them. Pretty sure when the zombies got close and slaughtered the infantrymen, the guys in the tanks just closed the hatch and started praying.