Just a little curious... has anyone run a mass combat in PBP?

If so how does it work?/ How did you run it?

I have not, but once upon a time, I had some rules for it.

I wonder what I did with them?

Pretty sure the 3.5 supplement Heroes of Battle covers that and I want to say I've seen rules for encounters like this elsewhere too.

Are you talking about players controlling a whole "unit" of troops rather than individual characters?

Yeah... rather than just play a character, that they have units of varying sizes....

Any mass battle I've run we pull out the old battle system stuff, and mini's and run a big battle...
I didn't know how it would work for PBP.

This might be interesting:
http://www.escapistmagazine.com/news/view/134080-Dungeons-Dragons-Next-Reveals-Mass-Combat-System-Details

It looks like the 5ed version of the original battlesystem But it will be nice to see a d20 version of the rules.

The Star Wars saga edition has a fairly streamlined system. Basically, you multiply the HP by four; keep initiative, perception, and defences the same; add 50 to the damage threshold; reduce the speed to 1 if the base character has a speed < / = 11, to 2 if the speed is between 12-15, and 3 if it is > / = 16; gain an attrition feature; gain DR 15; keep the same attack score; have a x2 damage multiplier; have all weapon attacks converted to area attacks; take half damage from all non area attacks; and keep feats, skills, and talents from the base character in it. It also has very specialized rolls for PC's within the units, but I usually just have PC's fill all the rolls to keep things moving well.