I just had a battle against three armies (Averus was helping), and it was great! Very fast paced. A bit confusing, but I'm sure me and Averus could help out any new people if we ran into them.
The bugs:
In battles against TWO enemies, I get no defeats and no wins, no matter what I do. Battles against one enemy works fine still.
That's all I've noticed, really, so far. I'll keep testing around.
Ideas:
Zones could be added to the battlefield: North Western Zone, North Eastern Zone, South Western Zone, South Eastern Zone, North Eastern Limit Zone, South Eastern Limit Zone, North Western Limit Zone, South Western Limit Zone, South Center Zone, and North Center Zone. With that addition, strategy would come into play. If the enemy has some archers, an army could go around the side and kill them while his friends army keeps the bigger army busy.
The ADVANCE command could then be replaced with NORTH, SOUTH, EAST, WEST. To retreat, one would have to move to his Limit zone and use the command RETREAT.
Instead of having a color for each zone, perhaps make all the areas white, and change the color of the zone to the color of the enemy occupying it. Your army could be, for example, RED, and your allies armies could be GREEN. The enemy could be BLUE. When more than one army was in a zone, a number could be added to the end to show how many were there. In example: W2, NW4, etc. If an enemy and an ally (or your army) was in the same place, it could show that a battle was going on between the two with a certain color... Orange, or something.
By now the map would be rather big and complicated, so instead of sticking it in the STATUS area, it could have it's own command, such as "battlefield", or "battlemap". Some people may just want to see how organized their army is without all that map in the way.
It's very difficult in the heat of battle to LOOK at an enemy army to see how many troops are in it. Could the number of troops be put next to the name somehow? That way you could just LOOK, without specifying, and see next to the names of the armies in the room how many troops are left.
If there are any uncommanded ally armies in the area, they could have a 50% chance to join in the fight and aid you. Same for the enemy armies. The thoughts behind 50% is that they may not see or notice the conflict (in an imaginary sort of way). This chance could perhaps change according to the season and weather. Rain might change it to a 40% chance, while clear skys might change it to a 60% chance, etc.
All this may be more complicated than a MUD needs to, or can, be.

As it is, the battles are quite good.