Mr. Ajami is a professor at the Johns Hopkins School of Advanced International Studies and a senior fellow at the Hoover Institution. He is co-chair of the Hoover Working Group on Islamism and the International Order.

The trail had grown cold, but the case for justice had never gone away. Osama bin Laden had warred against the United States, he had called on every Muslim "by God's will to kill the Americans and plunder their possessions wherever he finds them and whenever he can." He had erased the boundary in the laws of war between combatants and civilians, and he had set out the case that the age-old ailments of a deeply troubled Islamic civilization could be laid at America's doorstep.

He and his top lieutenant and partner, the Egyptian Ayman al-Zawahiri, had made sure that America would be caught in the crosshairs of a deadly civil war between their foot soldiers of terror and the Arab regimes in the saddle. The "near enemy" they dubbed the incumbents in Saudi Arabia, Egypt and elsewhere in the Arab world. The "far enemy" was the name they gave the U.S. It was halal, it was permissible, to war against the far enemy, to exploit its freedoms, in a campaign of vengeance against these regimes and the Pax Americana said to sustain them.

There was plenty of victimhood and rage in Arab and Muslim life, and this man of checkered background—Saudi citizenship, Yemeni ancestry on his father's side, a Syrian mother—found his themes as he went along. There was his mastery of lyrical Arabic, and it played to the gullible. There was the legend on offer of the man born to wealth but giving it all up in pursuit of a holy cause. In his run, his decade if you will, Arab political and cultural life was a scorched earth—terrible, plundering regimes, disaffected and sullen populations trapped in no-man's land, the absence of any hope of economic and political improvement. Some 300 million or so Arabs seemed cut off from history's progress.

Bin Laden and Zawahiri had little to offer that world, but what they presented, it must be conceded, had its appeals...