Why the fleet changes when you change the century

The five hulls are always the same lengths — five cells, four, three, three and two — because that is what makes the game Battleship. What fills them is whatever that navy actually had.

An 1870 fleet has no submarine and no aircraft carrier, so it does not get one. It gets ironclads and cruisers, and the smallest hull is a torpedo boat destroyer. By 1943 the longest ship on the board is a carrier and the battleship has been demoted to second place, which is roughly what happened.

The ships are picked by how well known they are

Each slot is filled by the most written-about ship of that type, that navy and that era — measured by how many languages have an article about it. It is a blunt instrument and it works: you meet Yamato and Bismarck and Hood, not the fourth destroyer of a class nobody has heard of.

It also means a famous ship turns up in more than one matchup, and that the same navy fields the same five ships every time. Both are the price of the fleet being real rather than generated.

A ship is easier to date than you would think, and harder

Deciding which era a warship belongs to sounds like looking up a year. It is not: most individual ships in the public record have no date on them at all. Of thirty-eight well-known aircraft carriers, nine carried one.

Their classes almost always do, because a class is a design with a year attached and a ship is one hull that somebody filled in halfway. So the era here comes from the class. It settles an argument too — there have been several USS Enterprises, and the one that fought at Midway and the one that ran on nuclear reactors are told apart by their class and by nothing else.