Chairman of the Joint Chiefs of Staff Gen. Mark Milley, asked about the relationship between the U.S. and Taliban going forward, given their recent and uneasy cooperation during the evacuation mission, offered a pragmatic view, without sugar-coating the militant group.

"We don't know what the future of the Taliban is. But I can tell you from personal experience that this is a ruthless group from the past, and whether or not they change remains to be seen," Milley said. "And as far as our dealings with them at that airfield or in the past year or so, in war, you do what you must in order to reduce risk to mission and force, not what you necessarily want to do."

Asked whether the U.S. might coordinate with the Taliban against ISIS-K, the terror group responsible for a suicide bomber attack last week which that killed 13 U.S. service members and 170 Afghans, Milley said, "It’s possible."

Defense Secretary Austin then chimed in, "I would not want to make any predictions."

Chariman of the Joint Chiefs of Staff Gen. Mark Milley vowed that the Pentagon will continue it counterterrorism efforts despite not having troops on the ground in Afghanistan, echoing President Biden's remarks from Tuesday in saying the U.S. mission has changed over time.

"For the past 20 years, there's not been a major attack on our homeland. And it is now our mission to ensure that we continue our intelligence efforts, continue our counterterrorism efforts, continue our military efforts to protect the American people for the next 20 years," he said.

Milley said that as of Wednesday morning, approximately 20,000 Afghans have arrived at eight different military bases in the continental U.S. and more refugees are on the way. Since the evacuation mission began, he said 124,334 people were airlifted out of Afghanistan by the U.S. and partners.

"Those 124,000, they never knew the 13 who died, and they will never know the 22 who were wounded or the thousands of dead and thousands of wounded who came before them. But they will now live in freedom because of American blood shed on their behalf," Milley said.

The top U.S. general closed his remarks with a message for service members.

"We're all conflicted. Feelings of pain and anger, sorrow and sadness, combined with pride and resilience," he said. "One thing I am certain of: For any soldier, sailor, Marine and their family, your service mattered, and it was not in vain."

Secretary of Defense Lloyd Austin spoke on the U.S. military’s withdrawal from Afghanistan after 20 years from the Pentagon on Wednesday, offering his thanks to U.S. forces and their families.

"We have concluded our historic evacuation operation and ended the last mission of the U.S. war in Afghanistan. America’s longest war has come to a close," he said.

Austin hailed the historic evacuation effort in an "immensely dangerous" environment over the past few weeks. He reminded that 2,461 troops were killed in Afghanistan, as well as the more than 20,000 injured -- "some still carrying the scars that you can't see on the outside."

“Our forces risk their own lives to save the lives of others. And 13 of our very best paid the ultimate price. Many of them were too young to personally remember the 9/11 attacks," he said. "The United States military will always honor their heroism."

Speaking directly to Afghan war veterans and their families, Austin said he understands it’s been a difficult time but said he hopes they can look back at the long conflict with "thoughtfulness and respect."

"I've heard strong views from many sides in recent days, and that's vital. That's democracy. That's America," he said. “As we always do, this department will look back clearly and professionally, and learn every lesson that we can."

"Right now, it's time to thank all those who served in this war," he added.

Russian President Vladimir Putin again poured scorn on the U.S. military’s 20-year presence in Afghanistan, saying on Wednesday the nation achieved “nil” in an attempt to “civilize the local people.”

"The only result is tragedies and losses for those who were doing that, the United States, and especially for the people who live in the territory of Afghanistan. This is a nil result, not to say a negative one," Putin said to teenagers at an educational facility in Russia.

Putin, who has previously said Russia has no plans to deploy troops to the country the Soviet Union once occupied but then was forced to retreat from in 1988 and 1989, claimed the U.S. approach to Afghanistan was flawed in that it tried to instill Western norms on Afghan people.

It is "impossible to impose anything from outside," he said.

Russia, as well as China, have not yet formally recognized the Taliban as Afghanistan's legitimate governing power but have generally shown more of a willingness to work with the militant group than have other nations.

-ABC News’ Tanya Stukalova