There are several ways that anarchy can come about, but anarchy is the step before communism/dictatorship.
It is the desire of the socialists in our country to create anarchy such that they can step in with a communist/dictatorship type of government. In the case of the socialists, anarchy would result from the total chaos of a true democracy with no formal leadership or regimented form of government.
The slow slide of socialism can lead to communism without anarchy. Anarchy can be the step that leads to communism and comes about by the lack of morals just as libertarianism without the foundation of morals will lead to a population that preys on each other...The fall of the Roman Empire.