"The power of the masses can topple autocrats."
Not by itself. In 1989, people power swept across Eastern Europe. Mass strikes in Poland brought the country's communist rulers to the table to negotiate their way out of power. After hundreds of thousands of people gathered in Prague's Wenceslas Square, one of Eastern Europe's most brutal communist regimes crumbled and handed over power in Czechoslovakia to a motley crew of playwrights, priests, academics, and friends of Frank Zappa. In East Germany, teeming crowds simply walked out of communism's westernmost showpiece to seek asylum in, and then reunification with, the West. And people power, as Ferdinand Marcos found to his dismay in the Philippines in 1986, was not limited to communism or Eastern Europe.
But there was far more to the collapse of communism in Eastern Europe and autocratic regimes elsewhere than the impressive moral authority of crowds. As the Chinese showed in Tiananmen Square in 1989, capitulating to pro-democracy activists in the streets is hardly the only option. There have been plenty of other places where people power has failed disastrously in the face of a well-organized military response. In Hungary, the popular uprising of 1956 was brutally crushed by Red Army tanks. Burma's 2007 Saffron Revolution produced little more than life sentences for the country's dissident Buddhist monks; Iran's 2009 Green Revolution fell to the batons of the Basij two years later.
What distinguishes people power's successes from its failures? Size, of course, matters, but autocrats tend to fall to crowds only when they have first lost the support of key allies at home or abroad. The Egyptian military's decision to abandon Mubarak and protect the protesters gathered in Cairo's Tahrir Square, for instance, was crucial to the president's downfall this February.
How can demonstrators persuade regime stalwarts to jump ship? In Eastern Europe, the geopolitical sea change engineered by Soviet leader Mikhail Gorbachev and his allies obviously helped -- but you can't exactly bring down the Iron Curtain again. Regimes with professionalized militaries separate from civilian authorities might be more vulnerable to defections; regimes based on highly ideological political parties are less likely to see their members break ranks. The credible threat of ending up at the war crimes tribunal in The Hague or having your Swiss bank accounts frozen can work wonders as well. But unfortunately for protesters, predicting authoritarian reactions to uprisings is far from an exact science -- which is little consolation when your head is being cracked by a riot cop.