After 20 years at war due to the events of September 11, 2001, President Joe Biden withdrew the last 14,000 troops out of Afghanistan.
On August 30, the U.S. withdrew from Afghanistan, but a week after the withdrawal the Taliban, which is the terrorist group the United States were fighting, took over Afghanistan in a week. And there is a difference between the Afghanistan army and the Taliban. The Afghanistan army was trained by the United States. And the Taliban is a rebel group harming the civilians that live in Afghanistan. Due to lack of food and supplies the Afghanistan army was not able to keep the conflict going and lost the territory.
Here is an NPR article you can listen to and follow and along and read too.
https://www.npr.org/2021/08/20/1029451594/the-afghan-army-collapsed-in-days-here-are-the-reasons-why