You have: Invasion or Usurping. I'm not 100% on the other methods, but I know these two have been used in the past and present.
Hitler used several methods to stay in power including fear, propaganda, and pride. Much of the country, especially the military, where quickly drawn into the false hope of a Utopian society.
The country that had great military power in the 1700's was Great Britain.
Military and econemy power
China
Superpower.
Military rule is a type of dictatorship in which power is held by one or military
absolute power
Joseph Stalin's military goal was to become a military power. He wanted to spread communism and make his country strong.
Propaganda, military police, a big army, and great manipulation skills.
Vietnam
He took power in a military coup in January 1971 while the President, Milton Obote, was out of the country.
Cuba