Every year, South Korean special-forces undergo serious winter training to strengthen their minds and bodies and to make sure the cold doesn't affect them on live missions. More than 200 rangers take part in the gruelling winter training session, in Pyeonghang, 180 km east of Seoul. They do gymnastics, swim in icy water, hurl snow at their bare chests, build snow shelters and sprint, all at temperatures of under -30 degrees Celsius. The extreme training lasts for nine days.