"Liberation" is not a term I would ever use personally, as it depends on a point of view. "Occupation" is equally valid. Ask the Baltic States, who found themselves alternately "occupied" and "liberated" by Soviets and Nazis from the 1920's until the 90's. If you do find yourself invaded, I fail to see what the sysytems of government has to do with it. Why should a republic get a free pass? Interesting idea, but can't see it playing out well in Port Stanley, despite Agentina being a republic and Great Britain being a monachy. Didn't count for much in the UN, or for that matter on the battlefied.