Okay, I KNOW this game had single player skirmish mode when it came out. I must be dumb though because I can't find it. The only options under single player are the campaign and custom missions, but the custom missions is just a blank list.

What am I missing?

I just started up a local MP match and added Bots

Huh. I remember there being a direct skirmish mode under single player in the original release. I guess Soviet Assault changed that?