When a remote outpost was raided, a U.S. Army squad was forced to move into the underground battlefield and waged a life-and-death battle in a new type of war that had never been seen before.This is not only a tactical subversion, but also a test of the limits of will and courage.They want to find light in the darkness, face fear in the unknown, shoulder the mission of high risks, embark on a journey full of uncertainty.