How were 20th century communism and fascism similar?

Communism arose as political philosophy with a distinct metaphysics and theory of history; it existed as only an ideology for over half a century before being put into practice. Fascism, on the other hand, arose as a series of policies and political attitudes held by nationalists of various countries during the 20th century.Despite being very different to fascism on paper, communism as a political reality shares many features. Nationalism is key to both ideologies. Members of a country have a firm and unfailing devotion to their homeland, whether it be Germany or Russia. This extreme patriotism justifies the conquest and destruction of ideologically opposed nations