In Orwell's Homage to Catalonia, he discusses the opposition for revolution from both the USSR and the Communist Party in Spain. Why is this? Specifically, why would communists oppose revolution and support the return to a capitalist democracy?

References to this are in chapter 5: "In particular the Communist Party, with Soviet Russia behind it, had thrown its whole weight against the revolution. It was the Communist thesis that revolution at this stage would be fatal and that was to be aimed at in Spain was not workers' control, but bourgeois democracy" (page 51)

"The general swing to the Right dates from about October-November 1936, when the U.S.S.R. began to supply arms to the Government and power began to pass from the Anarchists to the Communists. ... Consequently the Russians were in a position to dictate terms. There is very little doubt that these terms were, in substance, 'Prevent revolution or you get no weapons,' and that the first move against the revolutionary elements, the expulsion of the P.O.U.M. from the Catalan Generalité, was done under orders from the U.S.S.R." (page 53)