exchange. They did it in under a minute. Tonight, what really happens when the brave soldiers go behind enemy lines to rescue one of their own. Here's ABC's Martha Raddatz. All right. Reporter: An... See More
exchange. They did it in under a minute. Tonight, what really happens when the brave soldiers go behind enemy lines to rescue one of their own. Here's ABC's Martha Raddatz. All right. Reporter: An extraordinary encounter like no other we have ever seen. The end of a five-year search, a Taliban propaganda video showing an elite American team swooping over the hills in a especially modified blackhawk helicopter. Surveillance aircraft and backup forces overhead. On the ground, the enemy, 18 Taliban fighters. The two sides about to meet because of this man. The only am can prisoner of war held in Afghanistan, army sergeant Bowe bergdahl. His captors have brought him to this remote meeting site. A battlefield exchange. Taliban have soldiers with rpgs and machine guns. Our soldiers with assault rifles. Reporter: The pilots are watching Taliban rocket-prop rocket-propelled grenades. Powerful enough to take down those blackhawks. They're thinking this could be a trap. You can see the helicopter circled before it landed too. I'm sure they were looking to make sure that everyone was right. Once on the ground the years of planning now boil done to under one minute. Bergdahl carrying a bag is escorted by two Taliban across to three Americans dressed in civilian clothes who quickly approach. Obviously have got some kind of weapon. If they need to shoot across each other they're ready to go in case there is an ambush. Reporter: But the flag and number of men on each side have been prearranged by both side as a soon of trust according to the voice on the video. These kinds of exchanges you ask the other side to do a couple of things you. Can kind of verify that they're following the plan. Reporter: Amid the rapid greeting and hand shakes one American quickly runs his hand along bergdahl's back. That is not a friendly gesture. He is looking for a bomb, wires, something that would, would potentially make bergdahl a human bomb. He has been in captivity for five years. You don't know what his mental state is. You don't know if he is being coerced. Before the handoff, the Taliban video shows bergdahl in the back of a pickup truck. Head shaved, no beard, but blinking and hollow-eyed as if emerging from the dark for the first time. They want to keep him in the dark. If they're going to give him back to us. They don't want him to tell where the locations are. Experts say, bergdahl didn't know what was happening to him. He doesn't know if he was about to be released or something worse. He scud could be thinking. Leaning into bergdahl, one of the Taliban says don't come back to Afghanistan, you will not make it out next time. But take a closer look. It is a moment that might reveal something about the relationship he had with his captors. The Taliban reaches over and pats him, fairly gently, three times on the arm, like you and I have been together a long time I don't want to have to kill you next time you are here. Reporter: Within 25 second his American rescuers are gigd H -- giuiding him. One to walk with him, the other two walking backward. Not wanting to turn their backs on the Taliban until the final moments. They're watching. Checking their back. They want to make sure as they go out, that nothing is going to harm them. Reporter: Once at the helicopter before bergdahl can get on board, the white bag is dropped. Then, a second pat down. Why or what was in that bag may remany a mystery. Only bergdahl knows. Adrenaline is pumping. People are nervous. You don't know how it will go down. It's been smooth. For something to drop and somebody not to notice it could have been a mistake. Reporter: The video released to day will add to the other mysteries surrounding bergdahl's disappearance. Controversy has swirled since his release over how he was taken into captivity five years ago. Senior officials and soldiers who served with bergdahl tell ABC news he walked away from his base willingly. The army is preparing an investigation and wants bergdahl's side of the story as well. And the terms of the deal releasing five high-level Taliban from guantanamo in exchange for bergdahl have enraged some on capitol hill. These are wanted war criminals. It comes with some surprise and dismay that the transfers went ahead with no consultation, totally not following the law. Reporter: For others, bergdahl's release offers hope. I am a prisoner of the Taliban. Reporter: Video today emerged of a couple who disappeared while traveling in Afghanistan nearly two years ago. American Caitlin Coleman was 7 months pregnant and traveling with her Canadian husband when they went missing. I would ask that my family and my government do everything that they can to bring my husband, child, and I to safety and freedom. Reporter: The videos reportedly e-mailed to Coleman's father last summer and her family told associated press nay released the individually today in light of the publicity surrounding bergdahl's release and growing concerns about her health. She has a liver ailment. Which requires treatment. As for bergdahl, he remains at the German military hospital, and has still not spoken with his parents. While the hand-over may have taken just under a minute, his recovery will take much longer. But as he flew away from Afghanistan, and realized he was safe and in the hand of American forces, he broke down and wept. For "Nightline," I'm Martha Raddatz in Washington.
This transcript has been automatically generated and may not be 100% accurate.