President Joe Biden announced on Monday that al-Qaeda leader Ayman al-Zawahiri was killed in a U.S. drone strike in Kabul, Afghanistan.

Al-Zawahiri was known for working with Osama bin Laden in the plotting of the 9/11 attacks against the U.S. that killed nearly 3,000 people at the New York’s Twin Towers, the Pentagon in Washington, D.C., and in a downed flight in Pennsylvania in 2001.

“He will never again, never again, allow Afghanistan to become a terrorist safe haven because he is gone and we’re going to make sure that nothing else happens,” Biden said. “This terrorist leader is no more.”

The operation is a win for the Biden administration after a disastrous military departure from Afghanistan that included the deaths of 13 U.S. Armed Forces personnel and left behind millions of dollars of military gear to the Taliban.

The departure also led to concerns that al-Qaeda would rebuild its power in Afghanistan under the Taliban’s rule. Despite a long-term hunt for al-Zawahiri, his location had not been known for several years.

The situation recently changed when it became known to CIA officials that the al-Qaeda leader was staying at a safe house in Kabul. Al-Zawahiri was reportedly on the balcony of the location when he was taken out by a drone, avoiding harm to others in the building or area.

“We make it clear again tonight: That no matter how long it takes, no matter where you hide, if you are a threat to our people, the United States will find you and take you out,” Biden noted.

Al-Zawahiri was 71 years old. He had led the organization since bin Laden’s death and had been involved in the leadership of al-Qaeda for parts of three decades.