Five weeks after the Sept. 11 attacks, Osama bin Laden publicly commanded his foot-soldiers to ramp up the violence against American civilians. But five weeks before his death, he privately instructed his lieutenants to refrain from killing any civilians. Did the world's most notorious terrorist have a moral awakening and grow soft? Hardly. His unheralded tactical shift was purely strategic.

This month, the Combating Terrorism Center at the West Point Military Academy released 17 declassified documents that were seized from bin Laden's Abbottabad, Pakistan, compound in the targeted killing last year. These documents, coupled with his post-Sept. 11 admissions to the media, portray a leader painfully aware that terrorism was proving counterproductive.

In fact, the Sept. 11 attacks exacerbated each of bin Laden's grievances against the West. Instead of safeguarding the Ummah from Western encroachment, the raid provoked a global "war on terrorism" that killed countless Muslims internationally. It mobilized Washington to invade and occupy Iraq, increasing U.S. troops in the Persian Gulf by a factor of 15. It unseated the Taliban, the strictest exemplar of Islamist governance in the world. It sapped U.S. support for Palestinian statehood. And it strengthened Western relations with unpopular, American-allied Muslim rulers in Pakistan, Saudi Arabia and elsewhere. Meanwhile, nonviolent protest movements have scored tangible victories across the Middle East from Egypt to Jordan, Morocco and Tunisia. Even from his Abbottabad compound, bin Laden could hardly maintain the pretext thatal-Qaida terrorism pays.

Bin Laden accomplished little, but he died a wiser man. The evolution in his strategic thinking mirrors recent empirical discoveries in the social sciences. In 2006, I published "Why Terrorism Does Not Work," the first study to examine a large number of terrorist groups in terms of their political effectiveness. Contrary to the fabled image of terrorist "masterminds," they seldom if ever attain their strategic demands. My newer statistical research confirms — even after factoring out the relative strength of governments and perpetrators, and the oft-extreme nature of their demands — that across target countries, terrorism lowers the odds of government concessions.

Complementary results are found in public opinion data. In the face of terrorism, electorates are manifestly not cowed into appeasement and do not support more dovish politicians. Quite the contrary. Claude Berrebi and Esteban F. Klor have demonstrated that Israeli voters have historically shifted to right-bloc candidates such as Ariel Sharon and Benjamin Netanyahu. Christophe Chowanietz likewise determined that within France, Germany, Spain, the United Kingdom and the United States, the electorates have moved to the political right in direct proportion to the lethality of terrorist attacks, thereby empowering the hawks. The mere release of anal-Qaida videotape the weekend before the 2004 election boostedGeorge W. Bush's national lead by 2 percentage points over Sen. John Kerry, his comparatively dovish opponent. This is precisely why Democratic presidential candidates always fear an "October surprise."

States also suffer at the bargaining table when they prey on civilians. In a 1996 study, Robert Pape analyzed strategic bombing campaigns worldwide from the First World War to the 1990 Persian Gulf War, and found that governments reach an inferior bargain when their campaigns target the population. Similarly, military historian Caleb Carr has charted the success of empires and great powers based on their brutality toward civilians, concluding that "The nation or faction that resorts to warfare against civilians most quickly, most often, and most viciously is the nation or faction most likely to see its interests frustrated and, in many cases, its existence terminated." More recently, Kathryn Cochran and Alexander Downes investigated the effectiveness of civilian victimization campaigns on interstate war outcomes from 1816 to 2007. They found that while indiscriminate bombings, sieges and missile strikes may stamp out countless civilians, such assaults on the populace have not yielded superior political settlements.

In sum, a spate of emerging empirical research indicates that bin Laden belatedly got something right: Killing civilians was at best an unproductive instrument for achieving his strategic demands.

His inchoate appreciation for nonviolence accords with another major empirical finding in the social sciences. In a new book, "The Better Angels of Our Nature," Steven Pinker shows that international actors are laying down their arms. In fact, we are currently experiencing the most peaceful period in human history, notwithstanding sensationalist media stories to the contrary. This trend holds true across indicators of international violence ranging from homicide rates to genocide, infanticide, rape, slavery, torture, war, wife-beating — even animal cruelty. In a related work, "Winning the War on War," Joshua Goldstein details the global decline in armed conflict that began after the Second World War and accelerated after the Cold War. Fewer wars are starting, more are ending, and those that remain are smaller, more localized and less deadly relative to the world population.

Earlier this month, I attended the annual conference of the International Studies Association, and the scholarly consensus was that the reduction of international violence cannot be dismissed as an artifact of measurement problems with the data. Little consensus exists, however, on the underlying reasons why. In all likelihood, there are multiple causal mechanisms behind our newfound gains in physical security, ranging from globalization to nuclear deterrence to the worldwide expansion of democracy and international institutions.

But strategic calculations are central. Recall, bin Laden began to vacillate over terrorism only when he began to doubt its value. Violence in all its manifestations will continue to decline whenever other practitioners reach the same conclusion — hopefully sooner.

Max Abrahms is a postdoctoral fellow in political science at the Johns Hopkins University and author of "The Political Effectiveness of Terrorism Revisited." His email is maxabrahms@hotmail.com.