I'm in the mood for proposing you a new scenery, a Chilean analogue (I leave to you all to define how much similar) of what happened in Spain in July 1936. That is: Pinochet's coup, though supported by the CIA, etc. basically is a mixed failure (maybe assuming some other general whose name I do not remember at present is not killed before as per OTL), as some army commander do not join, much of the police supports the government, the leftist parties arm own militias. Just try to deduce the developments (possibile Cuban air bridge for reinforcements, Argentinian, Peruana nd Bolivian involvement, US naval blockade and military reaction, Soviet nuclear saber-rattling...).