shortly after his inauguration, nixon had ordered the preparation of a contingency plan, one that would hopefully bring the vietnam war to an end. operation duck hook was to include an invasion of the north itself and included a proposal to mine its major harbors. the plan had been shelved at the time as too extreme, but it was not forgotten. the u.s. navy had also been updating its own contingency plans for just such a mining operation since 1965. on 5 may, nixon ordered the joint chiefs to prepare to execute the aerial mining portion of the "duck hook" plan within three days under the operational title "pocket money".