Duck Hook

Duck Hook called for the possible-nuclear bombing of military and economic targets in and around Hanoi, the mining of Haiphong harbor and other ports, saturation bombing of Hanoi and Haiphong, the bombing of dikes to destroy the food supply of much of the population of North Vietnam, air strikes against North Vietnam's northeast line of communications as well as passes and bridges at the Chinese border, and air and ground attacks on other targets throughout Vietnam.

[2] An attachment to a memo from US National Security Advisor Henry Kissinger to Nixon asked, "Should we be prepared to use nuclear weapons?"

The memo warned that "Since we cannot confidently predict the exact point at which Hanoi could be likely to respond positively, we must be prepared to play out whatever string necessary."

[emphasis in original] A few days earlier, a document from two of Kissinger's aides, Roger Morris and Anthony Lake, stated that the President must be prepared "to decide beforehand, the fateful question of how far we will go.

This was reportedly because: At the same time that he cancelled Duck Hook, it seems that Nixon embarked on a new strategy to start a "series of increased [nuclear] alert measures designed to convey to the Soviets an increasing readiness by U.S. strategic forces," according to Kissinger aide Alexander Haig.