The Germans knew the airmen were alive, but they couldn't find them so they started murdering Serbian villagers, probably thinking the villagers would reveal where the pilots had hidden after a few dozen executions. Well, the Krauts were wrong.
After the war, in July of 1946 I believe, Gen. Mihailovich was executed by the Communists - "for treason".
Serbia was one of America's most loyal allies in both World Wars. In both wars, Serbia was surrounded by Austrian/German vassals, but she chose to fight on the side of the good... against all odds.