The last of 33,000 extra US soldiers sent to Afghanistan by President Barack Obama more than three years ago have left the country, the Pentagon says.
They were deployed with the aim of pushing back the Taliban and allowing Afghan government forces time to take over the security of their own country.
Some 68,000 US service personnel remain as so-called insider attacks by Afghan soldiers and police increase.
The Nato-led coalition has reduced joint operations in response.
US Defence Secretary Leon Panetta announced the withdrawal in a statement, saying an important milestone had been reached.
He insisted the surge had been a success, both in terms of driving back the Taliban and damaging its al-Qaeda allies.
Transition to Afghan security control was on track to be completed by the end of 2014, Mr Panetta added.