WTW%for an episode of political unity and stability with unquestioned political authority (opposite of "revolt," "riot," "civil war," and "unrest")

Some close terms might be Risorgimento, solidarity, and dominion.

Unification is close, but this term should also apply to currently unified institutions that become more peaceful and supportive.

Nationalisation is related, but typically refers to increasing the power of a state. This term implies increased support for authority, not necessarily increased use of authority.