Here is the full list of all 7 1000 Man General achievements.
Emerge victorious from the first battle.
Beat the final level.
Win a battle that started by you being outnumbered by at least 2 to 1.
Win a battle without losing any health.
Win a battle in under 5 minutes.
Win a battle with an enemy difficulty of 1.4x or higher.
Invigorate 1000 troops in a single battle.