I use "invasion" as a neutral term to mean what happens when a foreign army moves in and sets out to displace the existing regime. I don't use it to imply anything about whether it's a good thing to happen or a bad thing.

The Germans invaded France in 1949, the Allies invaded Germany in 1945. The former was a bad thing and an unjust invasion, the latter, though tragic, was a good thing to happen, and a just invasion. But in both cases it would have been wrong to prosecute people taking part in resisting those invasions for murder.