Conversation so far:
Was Babrak Karmal a communist?
Yes, Babrak Karmal was appointed Deputy Chairman of the Revolutionary Council, synonymous with vice head of state, in the communist government.
What was Babrak Karmal in prison for?
In 1953 Babrak Karmal was arrested because of his student union activities.

Question: What did he do to promote Marxism?
Self-contained rewrite: What did Babrak Karmal do to promote Marxism?