Um
Now, your nation may have intentionally done this, but traditional ship classes have destroyers as one of the smaller ships, battleships the largest, and cruisers acting as everything in between. The reason being that destroyers were made with torpedoes- powerful anti-ship weapons- that get in close using superior speed and mobility- something that a large ship struggles with. Cruisers, meanwhile, act as anything from larger, better armed and armored destroyers to smaller, slightly less powerful battleships. They're to take down enemy destroyers, cruisers, and aircraft with their moderate AA, guns, and armor. 

and Duck, if you get angry at me for disagreeing again, then go ahead and kick me from the roleplay. This is science fiction, and is generally an advanced- type roleplay, based on previous iterations of the series. If you dislike me disagreeing and not accepting everything, and won't put up with it, do tell me now. 

Based on factual, modern information of traditional ship roles, this is the sizes of ships from smallest to largest:
https://en.wikipedia.org/wiki/Destroyer
https://en.wikipedia.org/wiki/Frigate
https://en.wikipedia.org/wiki/Cruiser
https://en.wikipedia.org/wiki/Dreadnought (This was the battleship up until America became a world power, in which the 'superdreadnoughts' of the time were renamed to 'battleships')
https://en.wikipedia.org/wiki/Battleship