Welcome to Dongmakgol

A U.S. Navy pilot, Neil Smith, is caught in a mysterious storm of butterflies and crash-lands his plane whilst flying over a remote part of Korea. He is found by local villagers who nurse him back to health. Within the small village(Dongmakgol), time appears to stand still. They have no knowledge of modern technology, such as guns and grenades. All villagers are unaware to the conflict within Korea.Meanwhile, not far from the village, a platoon of North Korean and South Korean soldiers have an encounter, and the ensuing gunfight leaves most of the North Koreans dead. The surviving soldiers from the North manage to escape through a mountain passage. The North Korean soldiers, Rhee Soo-hwa (Jeong Jae-yeong), Chang Young-hee (Lim Ha-ryong), and Seo Taik-gi (Ryu Duk-hwan) are found by an odd girl Yeo-il (Kang Hye-jeong) who acts crazy. She leads them to the village, where to their astonishment, they find two South Korean soldiers Pyo Hyun-chul (Shin Ha-kyun) and Moon Sang-sang (Seo Jae-kyung). The South Korean soldiers who, have both deserted their units had also been lead to the village which is housing the injured U.S. Navy pilot, Smith by a different villager.The unexpected encounter causes an armed standoff that lasts for several days. The villagers have no idea what the stir is about, and wonder why the two sides are standing there pointing those "sticks" at each other. The confrontation ends only when a soldier holding a grenade is worn by fatigue and accidentally drops it. Another soldier heroically throws himself onto the grenade, but it does not explode. He discards the "dud" over his shoulder in contempt, and it rolls into the village storehouse and blows up the village's stockpile of corn for the winter. The remnants fall down from the sky surrealistically as popcorn.The two groups of Korean soldiers and Smith now have to face the fact that their quarrel condemned the village to starvation in the following winter. They help the villagers in the fields to make up for the damage they have caused, and even work together to kill one of the wild boars that trouble the village. Tensions between the two groups of Korean soldiers gradually lessen, though members of both sides are haunted by the memory of terrible things they have experienced during the war.While this is happening, Allied commanders, who have lost several other planes in the area, are preparing a rescue team to recover Smith, whom they mistakenly believe has been captured by enemy units and is being held at a hidden base. The plan: when the rescue team finds and recovers Smith, a bomber unit is to fly in and destroy the anti-aircraft guns they presume are sited in the village, which means that the innocent villagers are now in grave peril.The rescue team, led by their commander (David Joseph Anselmo), drops in by parachute at night, suffering heavy casualties from the rough terrain. They enter the village, and under the assumption it is a cover for an enemy base, begin roughing up toward the villagers. Despite the efforts of the villagers to conceal the Korean soldiers by disguising them as villagers, a firefight breaks out in which all the members of the rescue team but one are killed and Yeo-il is fatally wounded by a bullet. The only survivor of the rescue team, the Korean translator, is hit over the head by Smith and is captured by the villagers.Through the translator, the people in the village find out about the bombing plan. The North and South Korean soldiers realize there is no time for Smith to make it back to his base to stop the bombing. The only possible way to save the village, they decide, is to create a decoy "enemy base" using equipment from the rescue team parachute drop, so that the bombing unit will attack them instead of the village.Smith is sent back along with the surviving rescue party member so that he can tell the Americans that there is nothing in the village to bomb, in case they decide to send more bombers. Meanwhile, the decoy is successful, and the remaining North and South Korean soldiers die smiling while a barrage of bombs explode around them. The village is saved, but at the cost of the lives of the former enemies who had later become friends.

Question: How did the surviving North Korean soldiers survived?
Answer: Escape through a mountain passage