Afghan retreat: US formally withdrawing from its longest war

The United States formally begins withdrawing its last troops from Afghanistan on May 1, bringing its longest war nearer to an end but also heralding an uncertain future for a country in the tightening grip of an emboldened Taliban.

U.S. officials on the ground say the withdrawal is already a work in progress - and May 1 is just a continuation - but Washington has made an issue of the date because it is a deadline agreed with the Taliban in 2020 to complete the pullout.

The skies above Kabul and nearby Bagram airbase have been buzzing with more U.S. helicopter activity than usual as the pullout gears up, following the start Thursday of a concurrent NATO withdrawal.

Afghan security forces were on high alert for any possible Taliban attacks on retreating American troops.

The U.S. military said it had carried out a "precision strike" after an airfield in the southern province of Kandahar where it has a base was attacked.

The strike, which the military said destroyed more rockets aimed at the airfield, came after the base "received ineffective indirect fire" on May 1 afternoon that caused no damages.

"The Americans will formally begin their withdrawal from Afghanistan starting May 1 and the Taliban might increase the violence," Acting Interior Minister Hayatullah Hayat told top police commanders, according to an audio clip given to reporters.

Afghan Acting Defence Minister Zia Yasin said U.S. and allied troops will be leaving their bases and will gather at Bagram, the biggest American base in Afghanistan.

From there "they will go to their respective countries", Yasin told reporters.

The prospect of an end to the U.S. presence after 20 years comes despite fighting raging across the countryside in the...