Marine Corps Maj. Thomas Schueman’s quiet street in Rhode Island is a world away from Afghanistan, but he remains steadfast in his mission.

As Taliban forces took over Afghanistan’s capital of Kabul Sunday, Schueman was desperately trying to find a way out of the country for his friend and former interpreter Zak, one of the many still trapped as the government collapsed around them.

“He wasn’t just a translator, he was my brother, basically one of my Marines,” Schueman told “Nightline.” “I have a lifelong commitment to the people I serve and lead.”

He hopes to get Zak, who will only be identified as such in this report to protect his identity, and his young family to the airport and to safety. Schueman made call after call as the hours turned to days.

Within a few short weeks of American troops leaving the country, Afghanistan has fallen to the Taliban, an Islamic military insurgent group, in a stunning failure. This comes after 20 years of Americans fighting there and $2 trillion spent.

Nearly 2,400 Americans, 66,000 Afghan military fighters and over 47,000 Afghan civilians were killed in the decadeslong war.

Many wonder if the sacrifices of those who served had all been in vain. Afghans who remain in the country stand to pay the highest price as the situation there grows more urgent by the minute.

Six thousand American troops have now been ordered to head directly to Kabul to assist in the evacuation of U.S. personnel and Afghans who assisted the U.S. mission. Images of Chinook helicopters evacuating U.S. personnel from the country were eerily reminiscent of the fall of Saigon in 1975.

President Joe Biden announced in April that he would make good on the Trump administration’s negotiated treaty with the Taliban to withdraw all troops from Afghanistan. Just five weeks ago, he was adamant that what we have seen over the past few days would not happen.

Monday, amid growing criticism, Biden admitted the Taliban retook the country more quickly than anticipated, but stood behind his decision to leave Afghanistan.

“If anything, the developments of the past week reinforced that ending U.S. military involvement in Afghanistan now was the right decision,” he said. “American troops cannot and should not be fighting in a war and dying in a war that Afghan forces are not willing to fight for themselves.”

Afghanistan fell less than one month before the 20th anniversary of the Sept. 11 terrorist attacks, after which the U.S. invaded their country. Dubbed Operation Enduring Freedom, it led to nearly two decades of fighting, involving roughly 800,000 U.S. troops.

Schueman was one of them. No stranger to the sacrifices of war, he earned a Purple Heart while serving. And like too many soldiers, he lost dear friends.

In 2010, he met a young interpreter named Zak. Schueman said Zak saved his life many times.

Schueman has spent the last five years trying to help Zak get a visa to the U.S.

“I think it’s a very simple transaction. You serve with U.S. forces and we will provide you a visa,” Schueman said. “He served with U.S. forces, we did not provide the visa. I think that’s a betrayal.”

As the Taliban took province by province, Zak spent days in Kabul working to get documents in order for him, his wife and four children, all under the age of five — while Schueman worked from the U.S. to devise an exit strategy.

“What the Taliban does to people who work with the U.S., they execute them,” Schueman said. “So this is not a ‘what if’ kind of scenario, this is what will happen if we cannot get Zak to the airport and on a flight.”

It’s become a nightmare reality for Afghan refugees — one call, one day, one moment could mean the difference between life and death.

After hours of back and forth, Schueman got the call Sunday night that Zak and his family were finally beginning the hour, 20-minute walk toward the airport.

But that glimmer of hope was dashed when hours later Zak left this voice message: “We just are returning back to our apartment because there was gunshot fire everywhere,” … “That’s why we returned back to our house.”

“We’ve exhausted every course of action I can think of — it’s about midnight, we’ll stay with them throughout the night here and pray for them,” Schueman said in a video diary late Sunday night.

Despite the setback, Schueman is still focused on finding a way out for Zak and his family.

The U.S. has now approved transport for 30,000 at-risk individuals, including interpreters and their families, out of Kabul — but the logistics remain daunting.

As of Tuesday, the Taliban was guarding the only way into the airport, only letting foreigners pass. The group declared they’re in full control, setting up checkpoints throughout the city to separate locals from foreigners.

Zak and his family remain in Kabul but they continue to be hopeful that he will get on an airplane.

“Until I know Zak has his ass on a seat in an airplane, I have to continue to believe that that is going to be what happens,” Schueman said.