The Anti-Aircraft Gun is a Gunpowder unit available in the Modern Era.
These artillery tubes fire shells up into the air. Upon reaching a pre-set height the shells explode, sending an expanding ball of deadly shrapnel into any nearby aircraft. Anti-Aircraft (or "ack-ack") guns are quite vulnerable to attack from the ground: if left unprotected they can be easily destroyed by any enemy infantry or armed unit.
Anti-Aircraft Guns were developed specifically to counter air raids, this new terrible threat in modern warfare. They possess tracking devices which intercept any airplanes that attack targets within two tiles of the Anti-Aircraft Gun's current position; the repeating guns then deliver devastating damage to all aircraft. Note that you can't attack airplanes directly, since they always finish their turn in their base; instead, you must use the Intercept command, which this unit uses by default.
Their combat strength against land units is also decent, although not as powerful as front-line infantry units, and could even be used as such in extreme situations. They can even capture cities!
Anti-air weapons are essential in modern warfare. Build some as soon as you get access to them via Ballistics, and move them into strategic positions - defending your cities, or your advancing armies. Don't forget that each gun only has one interception attack per turn, which is wasted if the gun makes another attack before that, so keep them on alert to use their main defensive power, while attacking enemy ground forces with other units. Also, don't leave them alone against fast enemy units - they are easily wiped out by tanks!
Unique Unit Replacements