Underground escape routes funded by CIA
(TL;DR Biden just handed Taliban a back door into Pakistan)
At the height of the Afghan Mojahedin's war against the Soviet invaders, the CIA provided money for a very ambitious project.
A series of defence tunnels was built in 1986 near the town of Khost in the mountains of Paktiya province, a few miles from the border with Pakistan. The aim was to store weapons and create an underground field hospital as well as to provide shelter against Russian air attack.
Bin Laden, the son of a wealthy Saudi building tycoon, had been one of the first foreign Muslims to rush to Afghanistan - within a few months of the Soviet invasion in December 1979. He brought his engineers and equipment to help with the job.
Although evidence is slim that he ever took part in combat, he was known as a well-connected donor in Peshawar, the hot and dusty Pakistani city which was to become the capital of the Afghan resistance in exile.
https://www.theguardian.com/world/2001/sep/18/september11.afghanistan