You need to say when, where, by whom.
the domino theory
Vietnam was a domino in domino theory if communist expansion
The theory of the Communist Manifesto was supported by political parties that identified as communist or socialist, such as the Communist Party and Socialist Party. These parties promoted the ideas of class struggle, workers' rights, and the eventual establishment of a classless society.
The Communist view is that Communism has no classes and hence no role for government.
Karl Marx
The Domino theory was that if one country became communist, the countries surrounding it would become communist as well. It was a theory used in America during the Cold War to justify American intervention in other countries.
Karl Marx is considered the father of modern Communist theory. It is grounded in economics and critique of capitalism. He didn't speculate on what a communist society would be like (post-revolutionary society) so he cannot be considered a utopian philosopher and his Communist theory cannot be considered utopian. He was certainly not a fascist.
There are a number of flaws in communist theory. This include abolition of rights to inherit or own property and denying emigrants and rebels any chance of having properties which is confiscated among others.
Force has to be used to create a communist society
The Communist Party, which is known by several names throughout the world, which espouses Communist theory and doctrine.
Karl Marx
The domino theory was the idea that a world-wide communist movement would topple and take over foreign governments one by one and the fall of one free government would cause another one to fall. The theory justified the use of US military aid to help foreign governments prevent a Communist take-over.