CO

From Advance Wars - Wiki on Neoseeker

CO, or Commanding officer, is the human that controls the unit movement and Unit making of an Army. Depending on who you choose, the CO Power that you can use will be different. Or, if you're playing Advance Wars 2: Black Hole Rising or Advance Wars: Dual Strike you may also use a Super CO Power. In the first game, the player was the one telling the CO where to move the units. In the later games, the CO must decide where to move for themself. Each CO has a different preference on what types of units to use.