'Retrograde' National Geographic documentary captures the U.S. exodus from Afghanistan

A new National Geographic documentary is asking a crucial question: was the two decades and $2 trillion spent fighting terrorism in Afghanistan worth the sacrifice of thousands of Americans who died in the war?

'Retrograde' takes its title from the military term for leaving a war zone, which in this case meant leaving Afghan soldiers to fight the Taliban on their own.

"I feel like it's my job to put you in those places, put you in those helicopters, on the ground in the airport, and make you think about, 'what if that was me, or my sister, or my cousin, or my brother,'" director Matthew Heineman said.

Heineman has come under fire before in 'Cartel Land,' but filming an attempt to re-supply Afghan forces via helicopter was a different level of danger.

"It was terrifying, you know there was nothing I can do about it," Heineman said. "In those really, really scary moments all I can do is focus on my camera."

As scary a ride as this was, the time of the final exodus of the Americans from Kabul was even more challenging.

"I mean, it was the first time I've ever cried while filming. It was just unbearably sad," Heineman said.

He placed himself in the middle of the crowds desperately trying to get on those last U.S. planes.

"The Taliban was watching us a hundred yards away at gun point," Heineman said. "Isis was circling with suicide vests waiting to attack, which happened 12 hours later in the very spot where we were filming in."

The director was left asking a simple question that you'll be asking too.

"What have we done? How did we get here?" Heineman said.

'Retrograde' began as an inside look at a battalion of green berets and Eyewitness News entertainment reporter Sandy Kenyon said he came away from Heineman's film with new respect for the soldiers fighting this losing battle.

Various U.S. presidents on both sides of the aisle are heard but never seen in this film, which so dramatically illustrates the tragedy of their misguided policies.

'Retrograde' is from National Geographic Documentary Films and is available on Disney+, both owned by the same parent company as ABC 7.