I believe they are M109 Paladin self propelled Howitzers... not tanks. What's the difference you might ask, well I am not nor have I ever been a tank jockey or an ordinance man but from my experience in the Marines tanks are direct fire weapons and howitzers are indirect fire weapons. If you are fighting and are close enough to the enemy that your tanks are firing line of sight you'd pray you were with a howitzer unit... miles in the back.
Ride a bike, you really never know what you might find!