Editor's note: William Bennett and Seth Leibsohn are authors of the recently published book "The Fight of Our Lives: Knowing the Enemy, Speaking the Truth, and Choosing to Win the War Against Radical Islam." Bennett is a CNN contributor and a fellow of the Claremont Institute; Leibsohn is a managing partner with the consulting firm Leibsohn & Associates.
(CNN) -- Sixty-six years ago on May 1, Americans learned Adolf Hitler was finally dead. On May 1, President Barack Obama announced Osama bin Laden was killed. Until Sunday night, no international figure's death had been so sought since 1945.
Since the 1990s, bin Laden had declared war against the United States. By and large, most Americans did not take that declaration seriously until nearly 10 years ago, on that bright September day, made dark by bin Laden and his league of terrorists. But long before bin Laden's declarations and actions, terrorism had been directed against, and afflicted upon, Americans. Bin Laden's death is a welcome victory and much-hoped-for news in our long fight, but it is not the end of the fight.
Before September 11, 2001, terrorists and terrorism had struck at America, both at home and abroad. But September 11, 2001 was different in both scale and means. It was the worst terrorist act in the history of the world. And the world was changed. Even after Sunday evening's news, the world will remain changed by what bin Laden had wrought.
Terrorism, state-sponsored violence and the advanced technology available to radical Islamists and other extremists does not necessarily require a large organization to kill large numbers of Americans. One young man with a car packed with TNT, as Fouad Ajami pointed out in "The Foreigner's Gift," can kill massive numbers of Americans. And, unless and until the death of bin Laden is seen as a new beginning and a new seriousness in our war against radical Islam, more Americans will be killed. Let us hope that new beginning and seriousness commenced on May 1, 2011.
Several things are important to keep in mind just now, lest we think the war ended Sunday night.
1. Terrorism will not stop, take a break or recede with this news. Palestinian terror didn't stop when Yasser Arafat died; it didn't even stop when he supposedly renounced terrorism. A lot of fuel animates the Islamist complaint against America and the West: Bin Laden was one part of it.
2. Al Qaeda itself has metastasized far beyond bin Laden, in operations, in doctrine, in command. The terrorist movement of al Qaeda has long ago superseded bin Laden himself.
3. It is entirely possible we will see an uptick in terrorism in the name of al Qaeda. Terrorist operatives who affiliate under al Qaeda's brand will likely want to prove it is still alive and active.
4. Even if there were no al Qaeda terrorists, let us not forget, until 2001, no terror group killed more Americans than Hezbollah. Hezbollah was known as the A-team of terrorism and al Qaeda the B-team. The war is nowhere near over; indeed, Iran and Hezbollah are as strong as ever, and who knows what kinds of leaders are waiting to fill what kind of vacuum bin Laden's death has created.
5. Finally, although it has been the subject of a lot of criticism, let us say a word of praise for President George W. Bush's terrorism detainee policies (and, more important, reconsider the ending of such policies). Not only did they lead us to Khalid Sheikh Mohammed (the operational director of September 11), they led us to the compound where bin Laden and his couriers were living in Pakistan.
On Sunday, Obama completed a part of what Bush began. But there is still much to do, as there is still a great number of enemies -- lethal, amorphous, violent and widespread -- set on killing as many Americans as possible. Our enemies are confined to no region. They obey no rules. And they esteem death over life.
The president was right Sunday night when he said, "Justice has been done." But there is still much justice to undertake as there is still a great deal of injustice aimed at us.
The opinions in this commentary are solely those of William Bennett and Seth Liebsohn.