In UFO Online, players choose a faction to join and build and expand a base that acts as a hub in the fight for freedom. This is where mercenaries are hired and trained and where technologies and weapons are researched and added to the arsenal. Then it's time to take on the aliens in turn-based tactical battles. The player commands an army of specialists, each of which has their own class-specific skill tree. Only with the right combination of targeted research and carefully planned out tactics will the player come out of battle victoriously.