
Civ III's game-concept of culture can make maintaining a hold on battle-won territory quite difficult, since there's a high chance that the citizens of a captured city will long for their old culture, and unless you keep them very happy under their new regime, there's a good chance the city will spontaneously flip back to its old colors. (Of course, the other option is to roll forward and continue to crush their old civ, so there's less to long for. But that's very hard to do all at once, especially if you're a democracy, which gets impatient with war very quickly. Maybe switching to communism before a major invasion is the way to go.)
I'm not sure I like this insta-switching so much, especially since all the military units in a city simply vanish when a city switches allegiance through cultural influence. Where did they all go? Did they all decide to switch sides and disband? Did the citizens somehow quietly rise up and kill them all overnight? (But it was eight Panzer units!) It's not clear. I'd almost like it better if they remained in the city, but changed their colors.