I recall this same conversation happening last time this was posted. Ship classes are weird, like how the New Orleans class cruisers were originally the Astoria class... until Astoria sunk and they were renamed. Astoria was laid down and launched first, but New Orleans was commissioned first and got a lower hull number.

As far as I can tell, the Japanese system goes by the order in the armaments plan, regardless of which ship actually ends up being launched or commissioned first.

Anyone who's curious about this can read much the same conversation in the comments under both of the previous versions of this image, which are now its children up there at the top of the page.

Dawn_Hika said:

Had this convo in Ido's tweet back then, got told that Japanese do call them Kaga-class Battleship. Dunno why English speakers decided to change it to Tosa but hey, the more you know

https://ja.wikipedia.org/wiki/%E5%8A%A0%E8%B3%80%E5%9E%8B%E6%88%A6%E8%89%A6

English (or generally, western) speakers usually use the first ship laid down as the name ship for the whole class. Tosa was laid down in February, Kaga in July, so I'd wager that's why the class is usually known as Tosa-class in the west. Of course, things might go weird during production and the name ship might end up finished later (English wiki claims that'd be the case with Tosa/Kaga), but the rule usually holds. No need to look far - Koenig-class is named after the first ship to be laid down, but second to be completed.

My understanding is that Kaga is the nameship for Japanese speakers because she ended up the only ship to be completed - though this leaves an open question why Amagi-class was not given a similar treatment.

Rather than speculating, read DeltaNovemberAlpha's long comment on the previous version of this image.

Long story short: the IJN, USN and most other navies named their own ship classes after the first ship to be authorized for construction. In this case, Kaga. But for foreign fleets they don't usually have access to that information, and name the class after the first ship they become aware of. In this case, Tosa.

> (Cape Kaga Metal Remix intensifies...)

ngedh said:

Rather than speculating, read DeltaNovemberAlpha's long comment on the previous version of this image.

Long story short: the IJN, USN and most other navies named their own ship classes after the first ship to be authorized for construction. In this case, Kaga. But for foreign fleets they don't usually have access to that information, and name the class after the first ship they become aware of. In this case, Tosa.

Welp, looks like I made a fool of myself for not checking the comments you mentioned. Thanks for pointing my dumb ass that way, TIL. :)