Pinned post for Q&A 😀

Drachinifel needs to make a video on the basics of what, at least officially and on paper, defines each class of vessel in the first half of the 20th Century in general. Things like “Landing Craft”, “Submarine” or “Aircraft Carrier” (at least, pre-helicopter) are easily defined even by a layman, but what makes a cutter a cutter, a cruiser a cruiser, a destroyer a destroyer, a battleship a battleship, and a super heavy battleship a hotel?

Me: B5
Them: You sunk my battleship!!!
Me: Ahem....if you look closely at the little plastic ship you will notice its actually a Battlecruiser.
Them: This is why I never play games with you

Enemy Officer #2: Sir, There’s a line of battleships approaching at high speed off the port bow !
Enemy Officer #1 looking through his binoculars: No, those are battlecruisers.
Enemy Officer #2: Oh good, for a second there I thought we were in real trouble.

I get the distinct impression that the term battlecruiser became obsolete around the time HMS Hood was built, as battle-ships/cruisers seemed to have functionally blended together into the Fast Battleship concept, the same way medium/heavy tanks blended together into the Main Battle Tank.

British Royal Navy: "So what should I call you? Should I call you a battlecruiser... fast battleship...?"
Hood: "You can call me Susan if it makes you happy."

Now you've truly poked the hornets' nest Drach

I agree with your conclusion in the final section. A fast battleship is essentially designers looking at their previous/contemporary generation of battleship and saying "we want all of that, but faster". A fast battleship is a battleship that gains a distinct speed advantage, but without compromising the firepower or armor that allows it to match up against other contemporary battleships (either "fast" or "slow"). Invariably this means a substantial increase in displacement compared to the slower battleships, which we see with both Hood and Iowa. To me, the clear dividing line between a fast battleship and a battlecruiser is that the former is still clearly intended to be able to fight another battleship 1v1, whereas the latter is not (just giving the ship some marginal capabilities to not be instantly obliterated by a battleship, a la the German WWI battlecruisers, doesn't count).

As I mentioned on the Alaska-class video, my personal definition of a battlecruiser is similar to yours, but a bit more expansive in that I don't consider having the exact same gun caliber as the battleships to be a requirement. I consider just having substantially larger guns than cruiser size to be sufficient, which is why I include the Alaskas in my definition of BCs. In my opinion, any ship that is designed for the mission of "kill cruisers, run from battleships" qualifies as a battlecruiser. So my criteria for judging whether a ship counts are based on the two parts of that mission. In my own personal definition, a battlecruiser must:

1. Be easily capable of killing contemporary "standard" cruisers. This means it needs all of the following:
a. Much greater firepower than a standard cruiser through larger guns.
b. Armor to protect against standard cruiser guns of the time.
c. Speed comparable to contemporary cruisers.

2. It also needs to be incapable of matching up against a contemporary battleship 1v1, by being deficient in at least one of the following:
a. Number of guns.
b. Caliber of guns.
c. Armor protection.

If a ship fails #1, it's not powerful enough to be a battlecruiser. If a ship meets #1 but doesn't have any of the deficiencies listed under #2, it's a fast battleship.

This is an entertaining demonstration of what happens when you form various kinds of inadequate definitions. “A warship with battleship-grade guns which can exceed 25 knots” is laughably too broad, and “A warship with battleship grade guns which is not armored to resist its own guns” manages to be too broad and too narrow at the same time. “A warship with one fewer turret and less armor than the contemporary battleship but more speed” appears tempting because it may be that those things are true of battlecruisers and only of battlecruisers (so it’s not too narrow or too broad), but it still breaks the rule of fundamentality because it makes no attempt to explain what a battlecruiser actually is such that those things would need to be true of it. Only “A warship with battleship-grade guns designed to destroy enemy cruisers and, secondarily, support a battle line” actually explains why battlecruisers had the characteristics they did.
In this context, I think Montana and Iowa are both battleship designs, they just reflect two different directions a battleship design can take. Iowa looks at South Dakota and says, “More speed!” while Montana looks at South Dakota and says, “More firepower!” Both valid choices, but one of those choices gives you a ship that can keep pace with an Essex.

I am in love with the idea that (if Iowa or Hood are battlecruisers then) the Yamatos are also battlecruisers. At that scale, I think their corresponding battleship would have to be the entire island of Iwo Jima

Drachinigel: "I consider the Hood a fast battleship"
Some of us: H E R E S Y

I’ve long said “had Hood been build by the US, she would’ve been called a battleship and carried a BB hull number.  Had Iowa been built by the British, she would’ve been considered a battlecruiser”

It's like how there were light, medium, and heavy tanks, but then they went to the MBT plan, one tank to do everything with enough armour, enough speed, and all the gun. Hood was transitional, Iowa was the equivalent of the M1 Abrams.

As far as I can tell the class of “battlecruiser” is entirely reliant upon there being an equivalent class of capital ship with a slower top speed. Getting any more specific than this really just leads to heartache.

It’s a fine line. The Battleship New Jersey’s YouTube page has an interesting video on this topic as well.

Well Drach didn't just poke the hornets nest, he kicked it over and sprayed water on it just to be thorough.
there will be as many opinions and definitions as there are people willing to argue them.
Personally I do NOT regard the British I classes as BC's.  They were conceived, designed and built as Dreadnought Armoured Cruisers but used in roles outside their concept.
The German "BC's" of WW1 apart from Von Der Tann should be more properly be referred to by the phrase Drach coined 'Light Battleships" as they were designed to supplement the main battle line as therefore were armoured for this role.  But of course people will have their own opinions and that's perfectly acceptable.

"I can't believe you said "torpedo boat" without a trigger warning."
–love, The Kamchatka.

Seeing how the Hood was nearly the same size as the Bismarck, and had the same guns, while the Iowa class were the second largest battleships in the world, behind the Yamato class... ya, they were Battleships.

Great video. The Iowa reminds me of post WWII Main Battle Tanks. No need sacrifice firepower, armor, or mission flexibility when new tech will let you have it all!

I think the HMS Hood, became a Battle Ship due to modifications in the design.  The Iowas we're Battleships by design.