John Yoo: Ten Years Without an Attack

Mr. Yoo is a law professor at the University of California, Berkeley. He was an official in the Justice Department from 2001-03, and is co-editor of Confronting Terror: 9/11 and the Future of American National Security, just published by Encounter Books.

Ten years ago this week, I switched on the TV in my Justice Department office and saw United Flight 175 destroy one of the World Trade Center towers. Shortly thereafter, American Flight 77 crashed into the Pentagon. One of the passengers on board was my friend Barbara Olson, a noted author and political commentator, who called from the plane to warn us. Only the brave Americans on United Flight 93 over Pennsylvania prevented a fourth plane from reaching D.C.

As I left a deserted Washington that night, I witnessed the unbelievable—our capital's dark sky lit up by a burning Pentagon. But in the decade to follow, the most incredible thing to happen was this: nothing.

After 9/11, terrorism experts inside and outside the government all agreed that more attacks would come. The coordinated hijackings revealed our open society's vulnerability and displayed the resources, sophistication and determination of a deadly enemy. Al Qaeda had a committed, intelligent leadership, a safe harbor in Afghanistan with dozens of training camps and thousands of trained fighters, and an ideology that appealed to frustrated, oppressed men in the Arab world. It had a track record of returning to the same targets; it had tried to blow up the World Trade Centers with a truck bomb in 1993. No one would have predicted that George W. Bush, and his successor, Barack Obama, would succeed in preventing another successful and disastrous terrorist attack.

Looking back over the decade, the first clear lesson is the critical importance of Mr. Bush's decision to consider the struggle with al Qaeda a war...