The U.S. reviewed a contingency plan to use tactical nuclear weapons on North Korea if an incident, such as the North's attack on a U.S. spy plane in 1969, reoccurred. The attack killed 31 crewmen.

A private research institute, the National Security Archive at George Washington University, has disclosed a declassified document from the Richard Nixon administration.

The document includes details of Operation Freedom Drop, which was a plan to launch a nuclear attack on North Korea if it attempted a second provocation. The U.S. planned to use a maximum ten kilotons of nuclear weapons to attack 12 or more North Korean targets, 70 kilotons to attack 16 airfields and a similar amount to diminish North Korea's offensive capability.

The report forecast the operation would lead to U.S., South Korean and allied casualties at less than ten percent of the total defense force, with the number of civilian victims ranging from hundreds to tens of hundreds, depending on the scale of the attack.