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Talk of strategically defeating Al Qaeda is all the rage in the White House these days. Defense Secretary Leon Panetta used the "D-word" in July. President Obama declared in his new counter-terrorism strategy, "We can say with growing confidence… that we have put Al Qaeda on the path to defeat." Compared to the woeful state of the economy, terrorism has become the administration's feel-good story of the year.

"Defeat" is a big word. It is also dangerously misleading. Yes, the United States has made great strides in the last decade to harden targets, improve intelligence and degrade the capabilities of violent Islamist extremists. Osama bin Laden's death was a major accomplishment. But the fight is nowhere close to being won, and America's most perilous...