I'm considering creating a fictional military organization designed in a highly organized and militarized manner such as you might find with the Norse of the 9th century... if the Norse had developed space flight, tanks, and powered armor.
Some quick research left me with the impression that the rank structure of the Norse was very simple: King, nobleman, freeman, and slave. Rather than have slaves, I'm going to use "thrall" as the rank for anyone who doesn't enter the military.
I found 3 cultural ranks that could be used: Jarl, Heisir and Thegn; and I'm considering as an example having a Jarl command 3 "boats" of 30 soldiers each, each boat is commanded by a Heisir, and each group of 10 soldiers are commanded by a Thegn.
My question is, are there other existing "ranks" or "honor names" (I'm looking for the words) that could be used as military rank in a similar way? Please remember, my basic groupings are king, noblemen, freemen, and thralls.