North Korea threatens nuclear retaliation over US

North Korea fires 2 ballistic missiles as US sub arrives in S Korea
North Korea said on Thursday deployment of U.S. aircraft carriers, bombers or missile submarines in South Korea could meet criteria for its use of nuclear weapons.
N. Korea protests U.S. nuclear missile submarine visit by firing two short-range ballistic missiles
Korea threatens nuclear retaliation over US displays of military force as US sub arrives in S Korea
North Korea fires two missiles after US submarine arrives in South
North Korea fires two missiles after U.S. submarine arrives in South Korea
North Korea Fires Two Ballistic Missiles As US Submarine
North Korea threatens nuclear retaliation over US displays of military force

The Truman Administration was intent on avoiding a general war against China and the risk of Soviet intervention. The use of nuclear weapons would have undermined the Administration's policy, and thus the option was rejected.