Unify, Diversify, Define: Lessons from the War in Afghanistan

Li Hongmei    source：Council on Foreign Relations

The War on Terrorism: Global Experts Reflect on Lessons Learned Twenty-Five Years After 9/11

Roses on the South Pool ahead of a ceremony marking the 24th anniversary of the September 11, 2001 attacks on the World Trade Center at the 9/11 Memorial and Museum in the Manhattan borough of New York City, U.S., September 11, 2025. REUTERS/Kylie Cooper

Unify, Diversify, Define: Lessons from the War in Afghanistan

Twenty-five years ago, the United States was the victim of the 9/11 terrorist attacks and responded by launching a protracted twenty-year antiterrorism crusade in Afghanistan. That expensive war cost many lives, did not eradicate the Taliban or al-Qaeda, and should be viewed as a strategic and tactical failure. The current wars in the Middle East, including U.S.-Israeli military strikes against Iran, echo these previous actions and could weaken regional governance and breed new anti-American and anti-Israeli hatred—a catalyst to new extremism and terrorism.  

The long and costly Afghanistan War offered profound lessons for the world in the fight against terrorism. The first lesson is that, as terrorism is transnational and can spill over any border, countering terrorism requires collective action. Multilateral cooperation is necessary, and the United Nations should play the leading role.

Second, military tools alone cannot effectively eradicate the violent extremism that often fuels extreme nationalist sentiment. States should use economic, cultural, political, and diplomatic means together. For example, China advances security through domestic development as part of its antiterrorism practice. This practice has yielded positive results, with China having no terrorist attacks for several consecutive years. World leaders cannot end terrorism without addressing development imbalances, social inequality, and weak governance.

Third, a well-defined, limited strategic objective is key to successfully combating terrorism. In the Afghanistan War, the United States changed its goals from antiterrorism to reshaping the Afghan political regime; this loss of focus prolonged the war.

Last, there are no good terrorists or bad terrorists—all terrorists are the common enemy of humanity and threats to peace. As a result, pursuing double standards in counterterrorism or using terrorism as a tool of geopolitical competition is dangerous. Global terrorism is rising again, and in some regions, especially South Asia, the security situation is deteriorating. At the same time, global governance institutions have become dysfunctional and fragmented due to the Trump administration’s aversion to burden sharing or engaging in global counterterrorism cooperation.

In this new era of counterterrorism, states should take stock of these lessons and seek to bolster the international cooperative order, curb the unilateralism and power politics that bring instability, clearly define terrorism, tackle the societal and ideological drivers of extremism through development, and be wary of using force in a way that breeds new resentment and extremist ideology. Global powers should shoulder that burden and provide that security for this increasingly interconnected world.