-- The longest war in American history came to an end Sunday.
"Today marks an end of an era, and the beginning of a new one," said U.S. Army General John Campbell, commander of the International Security Assistance Force (ISAF). "Today, NATO completes its combat mission, a 13-year endeavor filled with significant achievements and branded by tremendous sacrifice."
Beginning less than a month after the Sept. 11th attacks with air strikes against terrorist and Taliban targets in Afghanistan, the U.S. presence in the country would grow to a peak of 100,000 troops on the ground in 2010. Nearly 20,000 Americans would be wounded, and more than 2,200 killed.
As the ISAF flag was ceremonially cased and the flag for the new mission, "Resolute Support," opened, 10,600 U.S. troops remain in Afghanistan.
"We'll continue to train, advise, and assist the ANSF and Afghan Security Institutions at the operational and strategic-levels so that they can sustain their hard-fought gains and win the war," Campbell said. "'Resolute Support' will serve as the bedrock of our enduring partnership with Afghanistan."
For the most part, U.S. forces will remain at a handful of bases in Afghanistan to conduct the specialized training. Current plans call for U.S. troop numbers to be reduced by half by the end of next year.
By the end of 2016, the expectation is that the only U.S. military presence in Afghanistan will be at the embassy in Kabul.
"These past 13 years have tested our nation and our military," President Obama said in a statement. "But compared to the nearly 180,000 American troops in Iraq and Afghanistan when I took office, we now have fewer than 15,000 in those countries. Some 90 percent of our troops are home."
The U.S. will also continue to provide Afghan troops with combat air support if they should come under attack from Taliban fighters. Though the majority of U.S. troops will serve as trainers, about 1,000 of them will be special operations forces capable of carrying out counter-terrorism missions against the Taliban if they pose a direct threat to U.S. and Afghan forces.
Over the last two years, American and NATO troops have been in a support role as Afghan troops took the lead for providing security inside Afghanistan. American troops mostly remained on their bases as Afghan troops patrolled the countryside and urban areas.
While Afghan troops and police have held their own against Taliban fighters, they have also sustained significantly high fatality rates that senior U.S. commanders have labeled "not sustainable." More than 9,000 Afghan troops and policemen have been killed fighting the Taliban over the last two years, more than four times the number of U.S. military killed in 13 years of fighting in Afghanistan.
The United Nations last week projected that civilian casualties would reach 10,000 in 2014.
It remains to be seen what the reduced U.S. troop presence will mean for maintaining security. Already, in rural areas like northern Helmand Province, Taliban fighters have retaken territory from Afghan troops where the U.S. once had a size-able troop presence.