For months, Nixon and Kissinger had threatened North Vietnamese leaders with grave consequences if, by November 1969 (the one-year anniversary of the US bombing halt Lyndon Johnson had initiated), they did not modify their demands at the Paris negotiating table. In case they resisted, Kissinger’s staff was working out the details of DUCK HOOK, which included several possible punitive actions including aerial mining of Haiphong harbor and the use of B-52s over North Vietnam.
