User blog comment:Owlfeathers0117/Faction Defense Listings - PLEASE READ/@comment-10905876-20150609164644

AIF:

The home islands are defended by an extensive network of fortifications called the "Pacific Wall". These fortifications utilize artillery emplacements, and major fortresses at cities and near vulnerable beaches. Most standard batteries have 204cm guns in turrets, and barbettes housing doomsday cannons in a disappearing mount. Major fortresses are typified by the Neviston Battery, and use a combination of guns and missiles. Inland cities will have an anti-air and anti-flying ship defense, with similar defenses to the Neviston Battery.

Most flying ship factories are armored, and either partially or fully underground. Most have an armored door to protect the entrance, which retracts when a ship leaves or enters. Haven't really determined a thickness, but it is pretty thick. If you check most of my commissionings of AIF ships, you'll see mention of armored doors retracting.

The submarine base known as Leviathan Base has torpedo turrets to keep away subs, and a sonar buoy system is planned.

Vent Gamma on Tenelapis is protected by three landed aerospace warships that have been converted to fortresses, along with some UAC weapons. I think that's all of it, though I think there are colonial defenses too.