The United States has completed its withdrawal from Afghanistan ending America’s longest war and closing a chapter in military history likely to be remembered for colossal failures, unfulfilled promises and a frantic final exit.

Hours ahead of President Joe Biden’s Tuesday deadline for shutting down a final airlift, and thus ending the US war, Air Force transport planes carried a remaining contingent of troops from Kabul airport.

Thousands of troops had spent a harrowing two weeks protecting a hurried and risky airlift of tens of thousands of Afghans, Americans and others seeking to escape a country once again ruled by Taliban militants.

In announcing the completion of the evacuation and war effort, Gen Frank McKenzie, head of US Central Command, said the last planes took off from Kabul airport at 3:29pm Washington time, or one minute before midnight in Kabul.

The airport had become a US-controlled island, a last stand in a 20-year war that claimed more than 2,400 American lives.

The closing hours of the evacuation were marked by extraordinary drama. American troops faced the daunting task of getting final evacuees onto planes while also getting themselves and some of their equipment out, even as they monitored repeated threats — and at least two actual attacks — by the Islamic State group’s Afghanistan affiliate.

A suicide bombing on August 26 killed 13 American service members and some 169 Afghans.

The final pull-out fulfilled Mr Biden’s pledge to end what he called a “forever war” that began in response to the attacks of September 11, 2001, that killed nearly 3,000 people in New York, Washington and rural Pennsylvania.

His decision, announced in April, reflected a national weariness of the Afghanistan conflict. Now he faces condemnation at home and abroad, not so much for ending the war as for his handling of a final evacuation that unfolded in chaos and raised doubts about US credibility.

More than 1,100 troops from coalition countries and more than 100,000 Afghan forces and civilians died, according to Brown University’s Costs of War project.

The Pentagon said that some Americans who wanted to leave Afghanistan were unable to make it to Kabul airport to board evacuation flights.

Gen Kenneth McKenzie, the commander of US Central Command, told reporters that the US believes it was able to evacuate the “vast majority” of Americans in the country who wanted to leave, but that it was aware of some who were could not depart.

Gen McKenzie said that in the final American flights out of Afghanistan: “We were not able to bring any Americans out.”

The last American civilians were evacuated about 12 hours before US forces left.

Gen McKenzie says the effort to bring out Americans will now fall on diplomatic channels.

The Taliban proclaimed “full independence” for Afghanistan after the last US soldiers departed.

Taliban spokesman Zabihullah Mujahid said that “American soldiers left the Kabul airport, and our nation got its full independence”.