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South Korean army soldiers aim their weapons during an anti-terror drill2 as part of Ulchi Freedom Guardian exercise, at Sadang Subway Station in Seoul, South Korea, Wednesday, Aug. 19, 2015. U.S. and South Korean forces launched Monday an annual joint military exercises, Ulchi Freedom Guardian, for a 12-day run to prepare for a possible North Korea's attack. (AP Photo/Ahn Young-joon)
South Korean army soldiers aim their weapons during an anti-terror drill2 as part of Ulchi Freedom Guardian exercise, at Sadang Subway Station in Seoul, South Korea, Wednesday, Aug. 19, 2015. U.S. and South Korean forces launched Monday an annual joint military exercises, Ulchi Freedom Guardian, for a 12-day run to prepare for a possible North Korea's attack. (AP Photo/Ahn Young-joon)

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    Source: U.S. was prepared to defend South Korea

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Source: U.S. was prepared to defend South Korea

Sources confirmed that the U.S. was making special preparations to defend South Korea in the event of an attack by North Korea. CNN's Barbara Starr reports.

Source: U.S. was prepared to defend South Korea

Sources confirmed that the U.S. was making special preparations to defend South Korea in the event of an attack by North Korea. CNN's Barbara Starr reports.