Domino theory
Domino theory is that if a country use the communist regime will result in the country around to follow. This is domino effect.
Domino theory are from the case of expansion of the doctrine and communist regime to expansion in Asia, China, North Korea and Vietnam because communist regime. It is believed that other countries such as Laos, Cambodia, Thailand, Malaysia, etc. is dominated in the communist system. Finally, the fall of the domino mean falling democracy.