User blog:Kevadu/Anti-aircraft Guns

There seems to be a lot of confusion out there about what different kinds of anti-aircraft guns were actually used for, and this has come up again in the context of the new AA cut-in section. So I thought it would be fun to write a blog post describing the historical uses of these different gun types and how that fits in with the KanColle game system.

Just what are all these guns types?
Historically there were actually as many as four classes of guns that could be found on a WWII-era capital ship. There were the main guns, intended to engage ships of similar size (battleship guns could take out battleships, heavy cruiser guns could take out heavy cruisers, etc.); a secondary battery for use against smaller ships such as destroyers or torpedo boats; heavy anti-aircraft guns that could take out aircraft at a distance; and light rapid-fire anti-aircraft batteries of machine guns or light cannons that would engage aircraft at close range.

Main guns were obviously the biggest, reaching as large as the 46cm (18.1 in) guns used by Yamato. Secondary guns could range from about 10cm (3.9 in) to 15.5cm (6.1 in). Heavy anti-aircraft guns typically ranged from about 75mm (3 in) to 130mm (5.1 in). Light anti-aircraft guns were usually heavy machine guns or automatic cannons in the 20-40mm range.

The way the heavy and light anti-aircraft batteries were uses were quite different. The light batteries were point defense weapons. They relied on rapid fire to deliver direct hits to incoming aircraft at relatively short range. The heavy batteries did not have nearly the same rate of fire, but they fired larger air-bursting rounds that could damage enemy aircraft even if they didn't score a direct hit. If you have ever seen a WWII movie or looked at actual photographs from WWII, the puffs of black smoke you see bursting in the air are coming from these heavy ant-aircraft batteries. See the picture above for an example. Aside from the different types of shells uses, the main advantage of heavy ant-aircraft guns was that they could effectively engage aircraft at much longer range than the light batteries.

Dual-purpose guns
You may have noticed from the cannon sizes I listed in the previous section that there's actually considerable overlap between the sizes of secondary batteries and heavy anti-aircraft guns. Well the people who designed these ships noticed that too. It was generally considered unlikely that a capital ship would have to engage both smaller vessels and aircfraft at the same time, so why not combine the two? This not only saves weight and space on the ship by not having to have two separate batteries, it also simplifies logistics by not needing to carrying rounds for so many different calibers of weapons.

Thus the dual-purpose gun was born. Simply put, it's a gun that could be used as either a secondary anti-ship weapon or a heavy anti-aircraft gun. Note that the term dual-purpose gun is often used interchangeably with the term high-angle gun. High-angle simply refers to the ability to elevate the gun barrel to point upwards. Strictly speaking a gun does not have to be high-angle to be dual purpose. Dual purpose refers to guns that have anti-aircraft fire control systems and a method to set the time fuze in the AA warhead. However it's undeniable that the most effective dual-purpose guns were also high-angle, because being unable to target aircraft directly above you is a pretty big limitation.

By WWII the US Navy, Royal Navy, French Navy, and Imperial Japanese Navy had all switched to using dual-purpse guns (though some IJN ships still carried dedicated anti-ship secondary batteries as well, such as Yamato's 15.5cm guns). This is the reason that despite all my talking about heavy anti-aircraft guns above you won't actually find any in KanColle. Though the switch to dual-purpose guns wasn't completely universal. The Kriegsmarine, for instance, still used dedicated secondary and anti-aircraft batteries.

Although originally intended as seconary weapons for capital ships, many destroyer designs (such as Akizuki) began using all dual purpose guns for their main armanent. And post-WWII as the age of the battleship came to an end guns mounted on naval vessels pretty much all became dual-purpose.

KanColle mechanics
There are two types of air defense in KanColle: Fleet defense and individual ship air defense. High-angle dual-purpose weapons contribute to fleet air defense. Dedicated anti-air weapons in KanColle all fall into the light anti-aircraft battery category and only contribute to the AA of the ship they are equipped on. I realize that to somebody not familiar with all of the above it might seem odd that dual-purpose weapons are apparently more effective than dedicated anti-air weapons, but really you should think of dual-purpose guns as representing heavy anti-air guns. They contribute to the fleet air defense because of their range. It's just that the IJN didn't have any heavy anti-air guns that weren't also capable of engaging surface ships.

Now with regards to the new AA cut-in mechanic, it also falls into the category of fleet air defense. And in that context it makes perfect sense that to trigger these cut-ins you need dual-purpose guns. Unless your ships are travelling in extremely close formation it's pretty unlikely that ship A is going to be able to shoot down aircraft attacking ship B with a machine gun.