
The troops handed over to Afghan forces on Sunday at camps Bastion and Leatherneck, in the southwestern province of Helmand. The timing of their withdrawal had not been announced for security reasons.
Their departure on Sunday leaves Afghanistan and its newly installed president, Ashraf Ghani, to deal almost unaided with an emboldened Taliban after the last foreign combat troops withdraw by year-end.
After Sunday's withdrawal, the Afghan National Army's 215th Corps will be headquartered at the 28sq km base, leaving almost no foreign military presence in Helmand.
The US military leaves behind about $230m of property and equipment for the Afghan military.
This includes a major airstrip at the base, plus roads and buildings.
Camp Leatherneck resembled on Sunday a dust-swept ghost town of concrete blast walls, empty barracks and razor wire.
Offices and bulletin boards, which once showed photograph tributes to dead US and British soldiers, had been stripped.
Heaviest fighting
The British experienced their heaviest fighting of the Afghan campaign in Helmand, losing hundreds of soldiers.
Their presence was boosted in recent years by US troops as the UK wound down its operations.
In all, 2,210 US and 453 British soldiers have been killed in Afghanistan since 2001, when the US-led coalition toppled the Taliban government shortly after the September 11 attacks.
AP/ZA