Is there any source (old or new) that gives a breakdown of how Rokugani typically structure their armies? I know it varies between clans, but details like units, ranks, and so on would be preferred.

Masters of War for 3rd edition rpg covered a lot of this, BUT it had an emphasise on Crab, Lion, and Unicorn clans. It went into great detail on the make up of individual armies in specific locations and roughly how many personnel would make up each unit.

http://l5r.wikia.com/wiki/Rokugani_Army

That might help. Indeed, clans have often special "forces" that aren't the typical military formation, but otherwise, everyone still follow in some way the good old Akodo structure.

Even the Shadowlands are organized, according to the first Crab diction.

Which I have to say is pretty refreshing that the Shadowlands forces are already past the point of mindlessly throwing themselves at the wall.

I'm a pretty patient person but having to wait until Junzo, or Yori, or Shahai, etc. finally, maybe turn bad before I see some actual leadership within the Shadowlands ranks would be pretty hard to go though again.

Which reminds me, I need to read those "Crab" fictions again.

6 hours ago, Ishi Tonu said:

Which I have to say is pretty refreshing that the Shadowlands forces are already past the point of mindlessly throwing themselves at the wall.

you will not want to see an Akuma no Oni throwing themselves at the wall. ?

Emerald Empire and Sword and Fan , both 4e supplements, go into great detail about the organization of armies.

The entire list of possible sources:

Way of the Dragon gives the Dragon organization.
Way of the Lion gives the Lion organization thaat is supposed to be the standard.

From the Clan War miniatures game the Crab Army Expansion Book has the Crab organization.

The Dragon Expansion partially reprints the Way of the Dragon information.

Kyuden Seppun has the Imperial Legions.

Emerald Empire (3rd ed version) kind of reworked everything.

Masters of War uodated Emerald Empirebut kind of left out everything but Carb, Lion and Unicorn. The were web updates that gave some information for the remaining clans and you can find them at Kaze no Shiro.

In 4th Emerald Empire and Sword and Fan you can find the latest information that hasn't changed greatly from 3rd Edition.

Personally I don't like any of them that much as far as the organization goes. I would like to see some more thought put in the interaction between Rokugan's mix of feudal and imperial organzation and having something based on, say, the Tang and Ritsuryō systems or something more based in the military structures of the late Muromachi/Azuchi-Momyama periods (particularly as seen during the Imjin war).