A South Korean soldier wear North Korea's military uniform, acting as North Korean soldier during an anti-terror and anti-chemical drill session held as part of the 2011 Ulchi Freedom Guardian (UFG) event on August 17, 2011 in Seoul, South Korea. The 11-day UGC, which features drills including the handling of chemical and biological attacks, is a regular joint exercise between US and South Korean troops to prepare for potential emergencies on the Korean Peninsula. (Photo by Chung Sung-Jun/Getty Images)

A South Korean soldier participate in an anti-terror and anti-chemical drill session held as part of the 2011 Ulchi Freedom Guardian (UFG) event on August 17, 2011 in Seoul, South Korea. (Photo by Chung Sung-Jun/Getty Images)

South Koreans firefighters and soldiers participate in an anti-terror and anti-chemical drill session held as part of the 2011 Ulchi Freedom Guardian (UFG) event on August 17, 2011 in Seoul, South Korea. (Photo by Chung Sung-Jun/Getty Images)