The attack on September 11, 2001, was part of a longer war. We had been fighting that specific war at least since our invasion of Iraq. We are still fighting it today.
Each side has had its victories. Al Qaeda achieved its stated aim: to get the Western coalition to remove our troops from Saudia Arabia. And they achieved their secondary aim: to terrorize the West and take Islamist fighting abilities seriously. We also gave them an unexpected victory by invading Iraq again. This wiped out the sympathy that the world had for the U.S. and against Al Qaeda. We created a massive recruiting field for Islamist terrorists, both in the Muslim lands and within the West. And by imprisoning and torturing whoever fell into our net, without charges or trials or law, we gave away the moral high ground. We will pay for these unforced errors for a long time to come.
For our part, the U.S. finally killed Osama bin Laden, and has severely damaged Al Qaeda. We offered the Taliban regime the chance to turn over Al Qaeda, and they chose not to. As a result, we removed the Taliban from Afghanistan, which was at the time the worst regime in the world (except North Korea). The unrelated war in Iraq removed Saddam Hussein and his family from power, which is a good thing, but at a huge cost to Iraqi civilians and to our relations with the Muslim world. Though there were gains from the Iraq war, I would call the balance of costs and benefits at best a draw.
In the long struggle, neither side is likely to prevail fully.
In the tit-for-tat with Al Qaeda following 9/11, though, we mostly won.
I think on this tenth anniversary we should declare victory and bring the troops home.