The planned withdrawal of all US and European troops from Afghanistan by September 11, 2021, will probably allow the Taliban to reconquer Afghanistan and impose a strict Islamist regime within the country, and establish terrorist organizations devoted to attacking the United States.
The Taliban followers are terrorists who are aligned with Al-Qaida, and they are the same groups who have launched terrorist attacks in the world over the past 30 years, including the September 11, 2001 attacks in the United States.
We need to keep adequate military forces in the region outside of Afghanistan to counter Taliban and Al-Qaida moves in Afghanistan and to keep them off balance to prevent attacks against us. Approximately 3,000 US troops should be based on the Arabian peninsula in case they are needed as a quick reaction force. US Special Forces in the region will probably have to be beefed up.
We need ground assault aircraft available in Saudi Arabia and the UAE. Additionally, a squadron of B-52s should be based in the region.
A US Navy carrier battle group and an amphibious assault force must be deployed in the region to provide the capabilities for air bombardment and missile attacks as necessary.
The Taliban are the enemy and must be treated as such.