I have just pushed some new changes regarding Defensive Forts which allows their destruction. With this comes HAT and Anti-HAT units.

More details can be found in the new help documentation on the matter, which states the following.

A Defensive Fort offers a defensive bonus to all units present at the position of such fort. You can see the percentage bonus of each level at the defensive fort page (accessed via HQ).

Defensive Forts can be destroyed by Heavy Attack Tanks (which are available in the Vehicle Workshop). If an attack containing Heavy Attack Tanks is sent to a position with a Fort, that Fort will be damaged according to the amount of sent HATs − the number of present Anti-HATs (see Counteracting HATs).

The level reduction to the fort is decided according to the following formula (limited to at most half the number of levels):

Number of HATs ÷ 2

When damage is done to the fort, all work on the fort will be forfeited and the resources lost.

Counteracting HATs

It is, however, possible to counter attack HATs before they do damage to the fort. This is done by the Anti-HAT ground unit, available in the barracks. A position can contain as many native and supporting Anti-HATs as possible, then, when the position is attacked by HATs, HATs will be destroyed at a 1:1 ratio by the Anti-HATs before they will do damage to the fort.

Resultant report of HAT attack: