Editor's Note: In light of the 21st anniversary of 9/11, we re-feature two recent analyses on the state of Afghanistan today, and how the risk of terrorism lives on despite more than two decades of U.S. efforts to quash it including the recent killing of al Qaeda mastermind Ayman al-Zawahiri. In Al-Zawahiri's Legacy, Part 1: How the U.S. Became al Qaeda's Top Enemy , we explore the July 31 death and legacy of al-Zawahiri, and how his death will impact the future of al Qaeda and jihadist ideology more broadly. In Why Terrorist Groups in Afghanistan Could Be Poised for a Resurgence , we discuss how despite al-Zawahiri's killing, a survey of foreign counterterrorism action in Afghanistan over the past year demonstrates foreign states' limited abilities to counter terrorist groups in the country — which may allow for an eventual extremist resurgence.