In the Forgotten Realms Campaign Settings is written that Archendale has the strongest army of all the Dales: 10 rides of 60 mounted warriors. Knowing that the Dalelands militia (RPG stats Archfiends or D&D Miniatures: Warband Generator ) are war1/exp1 the Archenriders should be at least level 2. I think the Riders should have similar stats, but do you think they could have fighter or higher warrior levels? Any quoted information could be very useful.
As a thought experiment, we first look at the text of the original boxed set that states:
Just to be clear here, the above descriptions should be sufficient to establish well lead forces with levels for their leader, on warhorses. If, however, you need specific breakdowns on the forces with an explanation for how those forces came to be, you could do worse than the Leadership feat series.
The most elegant solution would be to see if it is possible to get the 10 rides out of these three "PC" grade characters.
So, assuming that these three leaders have high charisma, they can muster around 120 men. A far cry from 600 mounted soldiers. On the other hand, a leadership score of 20 seems to be perfectly appropriate to one ride. If everyone takes "extra followers" each ride now becomes two rides. Necessitating 6 characters with a leadership of 20 (and a naturally occurring 5th level "leader" of each ride). I believe that leader feats also improve your leadership score. (reference)
This gives us a default package of: "Leadership, Improved Cohort, Extra Followers, Might Makes Right" for a bonus of +3+str making our total calculation +8+str+cha+level. Therefore we get the following hierarchy: