Soon after the last U.S. plane departed Kabul’s Hamid Karzai International Airport in the prep-dawn hours of Aug. 31, marking the end of America’s longest war, a Taliban spokesman posted a video message hailing “the result of 20 years of our historic sacrifices.”

“We left a historic chapter behind,” said Mohammed Naeem, according to a translation by CBS News. “The coming chapter is important.”

While U.S. officials broadcast the immediate security threats to efforts to evacuate Americans and Afghan allies in the chaotic final days of the war, they have been tight-lipped about what dangers may lie ahead. President Joe Biden defended his decision to pull U.S. troops from the conflict in a defiant address to the nation on Tuesday, noting that the terrorist threat to the U.S. has “metastasized across the world well beyond Afghanistan.” But the violent and harrowing withdrawal was a gift to terrorist groups looking to regroup there, experts say.