Commander

X-COM Commander

Commander is the highest rank that can be gained from any of your troops. Naturally, a commander accompanying your soldiers on a mission will provide some hefty moral boosts, or severe morale penalties if he or she is killed, so you may want them to hang back as a Rear Commander. When you have thirty soldiers or more (combined from all bases), and a vacant position, then the best eligible Colonel is promoted. There can only be one commander at any time.

Alien Commander

Commanders hold the loftiest position in the alien hierarchy. They can only be found in Alien Bases (Alien Colonies for TFTD), on Battleships (Dreadnoughts for TFTD) on an Alien Base mission, or on the alien's home planet of Mars (T'leth for TFTD.. Capture of a commander is crucial in order to complete the game. Only commanders are privy to the location of the Brain's stronghold on Cydonia.