Kim Jong-un recently said, North Korea had the military technology to miniaturize nuclear bombs and to mount them atop ballistic missiles. He has threatened to use them.
Every year America and Korea conduct military exercises in and around South Korea. These exercises are performed as a deterrent against North Korean aggression.
Remember this, the Korean War which lasted for 3 years from 1950 to 1953, was never over officially and there is no peace treaty signed by the North and South. The countries remain divided at the 38th parallel.
The North Koreans have a million man army on their side of the line ready to attack the South. There is always tension on the border. The threat of war is constant.
Because North Korea has recently tested an H-bomb (or so they claim) and because they launched a long range ballistic missile, the joint exercises this year is larger one than usual. About 300 thousand South Korean soldiers, along with 17,000 American soldiers are participating.
Kim Jong-un warns he will use nuclear missiles. (V.C)
nuclear warhead 核弾頭
mount atop 〜 〜に搭載する
ballistic missile 弾道ミサイル
conduct military exercises 軍事演習を行う
in and around 〜 〜の内外で
as a deterrent 抑止力として
38th parallel ３８度線