Things we believed during the Cold War that ended up being wrong

Yugoslavia was a major success story
They say hindsight is 20/20, and nowhere is that more uncomfortably true than regarding Yugoslavia. The nation (the six countries of Croatia, Bosnia, Serbia, Slovenia, Macedonia, Montenegro, plus the region of Kosovo) was seen in the Cold War as one of the few Communist success stories. Under Marshall Tito, Belgrade stood up to Stalin, kept open borders that allowed its citizens to come and go, and was generally seen abroad as place that was Socialist but acceptable. So keen on Yugoslavia's "soft Communism" was Washington that the U.S. poured billions of dollars into the economy to support it (via Foreign Policy). When Tito died in 1980, it seemed as if Yugoslavia would last forever.