When the Deathwatch was initially formed during the War of the Beast, it was set up as a singular Chapter. At this time, the Watch Commander was effectively the Chapter Master of the Deathwatch, with the first Watch Commander being Asger Warfist of the Space Wolves.[2a][2b]
Over time, the Deathwatch became a far more decentralised body, being deployed across the galaxy. Now based out of Watch Fortresses largely independent from each other, the title of Watch Commander stopped being a singular rank used to denote an overall leader of the Deathwatch. In the modern Imperium, the rank simply refers to the commanding officer of a particular Watch Fortress, generally a Watch Master.
- 1: Codex: Deathwatch (8th Edition), pg. 14 - The Structure of the Shield
- 2: The Last Son of Dorn (Novel)