how the hell i unlock other skirmish battle in single player? i've already finished theatre of war 3 times and played (and won) with both faction the only avaible single player skirmish map!

In skirmish mode, at the screen when you decide whether to play as attacker or defender, press START and you will have the options to change the map, number of players (1vs1, 2vs2 or 4vs4) and what faction attacks/defends on the map