Churchill is the one who really betrayed Mihailovich. He withdrew all support and chose to back Tito instead. The reason he did so was because Mihailovich backed off from attacking German targets in response to German reprisals against Serb civilians. Tito, being a communist, didn’t care about civilian reprisals. When it was pointed out to Churchill that supporting Tito alone would result in Yugoslavia becoming a communist country after the war, Churchill quipped “Do you intend to live there?”.
Churchill was a conniving sob.