PRAGUE — A quiz for history buffs. Twenty years ago — on June 4, 1989 — three events shaped a fateful year. Which do you remember most vividly, and which most changed the world?: (a) the bloody denouement of the protests on Tiananmen Square; (b) the death of Iran's revolutionary cleric, Ayatollah Ruholla Khomeini; and (c) the Polish elections.

Few would answer (c). The victory of the famed opposition trade-union movement, Solidarity, in Eastern Europe's first free election since 1946 was eclipsed by the violent crackdown in Beijing and Khomeini's tumultuous passing. Yet no single event did more to bring down communism in Europe — and thus to reshape the postwar international order.

The next few months will bring all sorts of commemorations of communism's end, particularly of the fall of the Berlin Wall in November 1989. To many, it was a glorious moment, emblematic of the West's victory in the Cold War, and one that seemed to come out of the blue. But if you watched the Eastern Bloc's disintegration from the ground, you would know that the process was far longer and more complex than most people realize.