The Royal Navy grouped the Tribals in flotillas identified by their class. An analogy with specialist military units helps explain the place of these ships within an already specialised force. Destroyer crews had to practise putting their ships between an attacker and a convoy or capital ship. At other times they had to close on a larger warship themselves.
Notable Point · 2:49-4:07
What set the Tribal flotillas apart
The separate Tribal flotilla designation went with a specialised role at the front of the destroyer force.