The Fleet was a militaristic humanoid species.
History
They devastated their own world in a series of wars and conquered 10,000 star systems. They moved their headquarters to another planet.
At the time the Thirteenth Doctor, Graham O'Brien, Ryan Sinclair and Yasmin Khan visited this other planet, the Fleet were building three new dreadnoughts in shipyards above it and were planning to attack the Avolantis System.
Space Lord Draal ordered to capture the Thirteenth Doctor and her companions. She reprogrammed Mark VI combat mechanicals putting an end to the wars led by the Fleet.
Biology and culture
The Fleet were famed for their eyesight. Their approach to carrying out war was unique in that they prepared paperwork before beginning a galactic war. They were ruled by the First Space Lord of the Admiralty. (PROSE: The Secret in Vault 13)