On Friday, Taliban forces reportedly captured four more provincial capitals—Qalat in Zabul province, Tarin Kot in Uruzgan province, Pul-i-Alam in Logar province, and Firozkoh in Ghor province.

In the last eight days, the Taliban have seized 16 of Afghanistan’s 34 provinces and 18 of its provincial capitals, as shown by the Statista infographic below.

The Afghan National Army (ANA) appears helpless to stop the advance, and videos have purported to show convoys of Afghan troops in U.S.-made vehicles retreating from major cities including Herat and Kandahar. ANA firepower and numerical superiority is counting for little.

Observers have been shocked by the speed of the Taliban offensive. The Washington Post reported that U.S. intelligence has warned the White House that Kabul could fall within 90 days of the full American withdrawal from the country on August 31.

The New York Times reported Friday that “American officials conceded that they greatly overestimated the ability of the Afghan national forces to hold off the Taliban for at least a year or so.”

Bill Roggio, a senior fellow at the Foundation for Defense of Democracies and editor of the Long War Journal, wrote on Twitter Friday: “The rout of the Afghan government & military is on.”

“With Logar under Taliban control, the Taliban is on the doorstep of Kabul. The siege will begin soon.”

Meanwhile, former ISAF commanders are expressing their dismay.

Former U.S. Afghanistan commander and retired Gen. David Petraeus said of the imminent American exit: “I said in the beginning that I feared that we would come to regret this decision… I didn’t fear that we would regret it as soon as I think we are now because this situation is seriously dire.”

Egon Ramms, a retired four-star German general and ex-commander of the Allied Joint Force in Afghanistan between 2007 and 2010, told Deutsche Welle he was surprised by how fast the situation has deteriorated.

“The Taliban are moving forward in a very, very quick way where I say that is astonishing for me,” Ramms said. The former general said the U.S. withdrawal plan was a “mistake,” though also criticized the performance of the ANA.

“We have trained the Afghan National Army and the Americans especially have equipped them quite well. So from that point of view, the question I have is, what is the Afghan army doing right now?”

“What are those old soldiers, around about 200,000 doing right now with the equipment and with the training they have got from the Americans, from the Germans to other nations in the past periods?”

Retired Gen. Sir Richard Barrons, who was head of U.K. Joint Forces Command in Afghanistan, told the BBC that the decision to withdraw from the country had “sold the future of Afghanistan into a very difficult place,” sending a “really unfortunate message” to Western allies.

The withdrawal indicates “we don’t have the stomach to see these things through, and we would rather leave than ensure that a humanitarian or political crisis doesn’t occur,” Barrons said. “We will run the risk of terrorist entities re-establishing in Afghanistan, to bring harm in Europe and elsewhere…I think this is a very poor strategic outcome.”

Former U.S. Ambassador to Afghanistan Ryan Crocker was also scathing of the withdrawal. He told CNN that the U.S. bears “major responsibility” for the Afghan military’s ongoing collapse, blaming former President Donald Trump for opening talks with the Taliban during his term.

General Arnold Punaro, a retired two-star Marine Corps Major General and the former staff director of the Senate Armed Services Committee, told Newsweek Friday: “What is happening was very predictable… I don’t think people felt like it was going to happen as quickly as it has.”

Publicly, the U.S. remains behind its allies in Kabul. Secretary of Defense Lloyd Austin spoke with President Ashraf Ghani on Thursday to “stress the United States remains invested in the security and stability of Afghanistan in the face of violence by the Taliban,” according to a read-out from the Department of Defense.

But reports on Thursday claimed Austin and Secretary of State Antony Blinken had privately asked Ghani to resign. The State Department later dismissed those reports.

The U.S. is sending 3,000 fresh troops to Afghanistan to support a partial withdrawal of American staff from the embassy in Kabul, though State Department spokesperson Ned Price stressed this did not represent an evacuation or full withdrawal.

Many observers have noted the similarities between the Taliban advance and both the collapse of Iraqi forces in the face of Islamic State forces in 2014, and the fall of Saigon—now Ho Chi Minh City—to North Vietnamese troops in 1975.

Punaro, who served as an infantry platoon commander in Vietnam, told Newsweek there are clear similarities between America’s defeat in that war and the apparent collapse of the Afghan government.

“Our military has a sophisticated system of lessons learned, and they did know the lessons learned. But sometimes they forget to go back and read the lessons learned. There’s some of that going on here.”

Ghani’s government has offered the Taliban a power-sharing agreement in an effort to stop the fighting, but the advance continues. The U.S. and European Union have both warned the Taliban of “isolation” if they take control by force.

But the Taliban have been isolated before, and are sure to find friends less troubled by their brutal authoritarianism.

“Why would they not take over after Afghanistan?” Punaro said. “They ran it before, that’s their intent, they want to recreate the Islamic state. Why are they going to stop short of it? I don’t see any reason why they would.”