WASHINGTON – As the August 31 deadline for a U.S. withdrawal from Afghanistan draws nearer, the Pentagon has stepped up the evacuation rate from Kabul Airport and flown 21,600 people out in 24 hours, Defense Department officials said Tuesday. But bottlenecks in the system and President Biden’s insistence that all troops leave the country by the end of the month could prevent the military from maintaining this pace.

The race against time means that the 5,800 Marines and soldiers at Hamid Karzai International Airport must try to evacuate thousands more Americans and Afghan allies, only to come out themselves over the next seven days to find the rubble of the 20 Years War in Afghanistan to eliminate somehow.

That process began on Tuesday when Pentagon spokesman John F. Kirby said several hundred headquarters, maintenance and other support forces not strictly necessary for the escalating evacuation operation had left the country.

Defense officials do not say publicly, however, which is becoming increasingly clear: some people are being left behind.

Since August 14, when Kabul fell to the Taliban, more than 70,700 people had been evacuated from Afghanistan by Tuesday evening, Biden said.

That is significantly less than the number of American citizens, foreigners and Afghan allies trying to get out. “We’re trying to get as many out as possible,” said John F. Kirby, the Pentagon’s main spokesman. He said American troops at Kabul airport “wanted to continue this pace as aggressively as possible”.

But despite all of Mr. Biden’s persistence in meeting his withdrawal deadline, neither the Department of Homeland Security nor the Department of State have been able to increase review and processing times to the extent necessary to meet demand.

A US official said it took up to 12 hours for immigration officers to screen arriving Afghans at Al Udeid Air Base outside Doha, Qatar against the National Counter Terrorism Center watch list. The official said that the verification and screening processes need to move faster to prevent the evacuation pipeline at Al Udeid, the largest base receiving Afghans, from re-clogging, as it did for several hours last week.

The Taliban have warned of “consequences” if the US military stays past the deadline. And on Tuesday, a Taliban spokesman said the group’s militants were physically preventing Afghans from going to the airport.

The Pentagon has opened military bases in Virginia, Texas, Wisconsin and New Jersey to temporarily house Afghan refugees and is likely to add more in the coming days, officials said.

Updated

Aug. 24, 2021, 9:51 p.m. ET

Kirby said US Afghan allies who fear Taliban reprisals are still being handled at Kabul airport, despite the airport gates being closed several times over the past week due to the onslaught of people.

The United States will continue to evacuate Afghans until the final days following the withdrawal of troops and equipment. Dozens of Afghan commandos – trained by the US – are also at the airport and have to be evacuated.

Understanding the Taliban takeover in Afghanistan

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Who are the Taliban? The Taliban emerged in 1994 amid the unrest following the withdrawal of Soviet forces from Afghanistan in 1989. They used brutal public punishments, including flogging, amputation and mass executions, to enforce their rules. Here is more about their genesis and track record as rulers.

Who are the Taliban leaders? These are the top leaders of the Taliban, men who for years have been on the run, in hiding, in prison and dodged American drones. Little is known about them or how they plan to rule, including whether they will be as tolerant as they say they are.

What is happening to the women of Afghanistan? When the Taliban was last in power, they banned women and girls from most jobs or from going to school. Afghan women have gained a lot since the Taliban was overthrown, but now they fear that they are losing ground. Taliban officials are trying to reassure women that things will be different, but there are indications that they have begun to reintroduce the old order in at least some areas.

For the military, part of the problem is that so many people are being promoted so quickly and with so little notice. For example, the C-17 military aircraft, which carry 400 people per load, have one or two toilets, and the flight from Kabul to Qatar takes four hours.

Once the flights arrive at Al Udeid in Qatar and other intermediate bases in the Middle East and Europe, the evacuees will be screened by Homeland Security and State Department officials who will determine if they qualify to enter the United States.

The military takes the Taliban’s red line seriously on August 31, also because some of the group’s commanders are cooperating with the US military and giving many people access to the airport, despite harsh speeches from Taliban spokesmen. In addition, the American military and the Taliban are cooperating against the threat of attacks by the Islamic State.

But after August 31, all bets will be gone, a senior US official said.

With so many people at Kabul Airport, Doha and other bases, concerns about sanitation, food and water are growing. The C-17 planes bringing refugees from Afghanistan turn around bringing in additional dumpsters, portable hand washing stations, refrigerated trucks to keep the water cool, and food and water.

Three babies were born to evacuees in the past four days, Defense Department officials said. A woman went into labor on Saturday during a flight landing at the Ramstein air base in Germany, officials from the air force said. The aircraft commander descended to a lower altitude to increase the air pressure in the jet, a decision officials said saved the mother’s life as she had low blood pressure. When the plane landed, paramedics rushed on board and gave birth to the baby – a girl – in the hold. All three babies are in good shape, Mr. Kirby said Tuesday.

After receiving a secret briefing Monday night, Adam B. Schiff, a California Democrat who heads the House Intelligence Committee, said the August 31 deadline for US troops to withdraw from Kabul was unrealistic.

“I think it is possible, but I think it is very unlikely,” Schiff told reporters. Using the abbreviation for special immigrant visas, he added, “Given the number of Americans who have yet to be evacuated, the number of SIVs, the number of other members of the Afghan press, civil society leaders, female leaders – it’s hard me I can imagine that all of this can be achieved by the end of the month. “