Chapters were a subgroup of a Legion, Mr. Timeline.

Legion-Chapter-Battalion-Company-Squad.

The space-knight motif was a part of their original design just as the Legion was. Hell, the Dark Angels, Legion I mind you, took the feudal world Caliban as their home and many of them were literally knights… Cypher.

It wasn’t as strong a motif, but guess what also developed as a tradition over the Crusade era?