What does it mean to seize power by force?

Answer 1

Perhaps the word you are looking for is Cu De Ta? Or, Coup d'état.

(pulled from wiki)

A coup d'état (pronounced /ˌkuːdeɪˈtɑː/, us dict: kōō′·dā·tâ′), (plural: coups d'état) or coupfor short, is the sudden unconstitutional deposition of a government, usually by a small group of the existing state establishment-typically the military-to replace the deposed government with another, either civil or military. A coup d'état succeeds when the usurpers establish their legitimacy if the attacked government fail to thwart them, by allowing their (strategic, tactical, political) consolidation and then receiving the deposed government's surrender; or the acquiescence of the populace and the non-participant military forces.

Answer 2

Coup, a putsch, or an overthrow and also know as a coup d'etat is seizure of power by force. It is considered successful when the usurpers establish their dominance.