September 11 Attack Anniversary: A Colossal US Failure

In 2001 an international coalition led by the US invaded Afghanistan. The Taliban regime which then controlled the government was removed from power and a new government was formed.

At the height of the conflict that followed there were more than 130 thousand NATO troops on the ground. 3,500 coalition troops were killed in the action, 70, thousand from the Afghan security forces, and tens of thousands of civilians.

Now more than 20 years after the conflict the Taliban again controls Afghanistan. So how did this war begin, why did it last for so long, and why is it considered one of the biggest U.S. failures?