BERLIN -- Once events make their passage from news of the day into history books, it is hard to imagine that they could have happened any other way. They're history, after all. And 20 years later, the fall of the Berlin Wall seems like that kind of history -- a world-changing event that we commemorate and celebrate, its heroes and villains well established, its images and significance clearly comprehended.

But the real story of the wall coming down is a lot less tidy than it may appear in the rear-view mirror. The "decision" to open the border was not a conscious choice at all. Instead of a reassuring victory for the forces of freedom, it was a chaotic and potentially violent mess. One of the most momentous events of the past century was, in fact, an accident, a...