Nocturian

really? damn, i didn't knew that, are talking about pre codex astartes or the actual one that is written in it.

a chapter of the codex astartes is approximately 1000 marines give or take the legions pre heresy were approximately 100,000 strong give or take at their peak chaos marines of the modern day have no number of troops for their ranks though many of the still strong at the end of the heresy would have around the hundred thousand such as the word bearers who retreated in order and thus preserved most of their numbers 

Aye, that makes sense, word bearers are also one of the most disciplined chaos traitor legions if I am not mistaken, only the black legion has more discipline in that sense.