Can I get steam achievements when playing only vs. AI opponents?

I've played a couple of games of DEFCON vs. AI opponents and I'm pretty sure to have met some achievements goals. Strangely those achievements haven't been unlocked. Are achievements allowed in vs. AI only mode?

You can get achievements in AI mode for some games. It depends on the game. For Counter Strike you can get almost all achievements playing with bots except the ones where they specify some special requirements.

In your case as can be read from the forum posts here on the Steam forum for the game Defcon

• http://forums.steampowered.com/forums/showthread.php?t=2467865
• http://forums.steampowered.com/forums/showthread.php?t=2476267

The achievement Santa is the only one that was unlocked with bots. So you will have to play against non AI opponents to unlock the other achievements.