The correct answer is : coup d'etat.
A coup d'etat is a putsch - a sudden and violent overthrow of an existing government by small group. To be able to perform the coup some control of existing military forces and the police is required. The change of power happens at the top, meaning only the leading government personnel is being replaced.
Coups were a regular occurrence in Latin America in the 19th and 20th centuries and in Africa after many countries there gained their independence in the 1960s.