But if there are no legal targets for the AP, the overrun combat ends two rounds after the Ogre's larger weapons are destroyed. And each turn lasts only two minutes. The Ogre can pick one enemy, head for it, and run it down, but it can't scoot all around that mile-wide circle squashing things. That's what it has guns for. Any structure with a defense strength has that strength doubled in a town.
Smaller structures get no benefit from forests.
The reference card and the text do not agree about the strength and range of Militia. Ramming takes place once, at the end of the first fire round. Large structures may have up to two PD installations. Each one adds 10 Structure Points to the building's total. When infantry are involved in an overrun attack, the rules say that each squad fires and defends separately.