As I understand it, you can gradually and deliberately increase support for either Fascism or Communism (or democracy where applicable) within any country in the game until, eventually, a civil war breaks out.
When that happens you can choose which political faction to support, changing your national ideology. You still have to deal with the loyalists though, but the proportion of soldiers on either side is dependent on the ratio of support each faction had before the conflict.
When that happens you can choose which political faction to support, changing your national ideology. You still have to deal with the loyalists though, but the proportion of soldiers on either side is dependent on the ratio of support each faction had before the conflict.