On the evening of April 30, 1970, President Nixon announced that the United States was going to attack North Vietnamese and Vietcong sanctuaries which were threatening allies from the Vietnamese-Cambodian border:
Tonight, American and South Vietnamese units will attack the headquarters for the entire Communist military operation in South Vietnam. This key control center has been occupied by the North Vietnamese and Vietcong for 5 years in blatant violation of Cambodia’s neutrality.
This is not an invasion of Cambodia. The areas in which these attacks will be launched are completely occupied and controlled by North Vietnamese forces. Our purpose is not to occupy the areas. Once enemy forces are driven out of these sanctuaries and once their military supplies are destroyed, we will withdraw.
These actions are in no way directed to the security interests of any nation. Any government that chooses to use these actions as a pretext for harming relations with the United States will be doing so on its own responsibility, and on its own initiative, and we will draw the appropriate conclusions.
He then spoke right to the American people, and succinctly provided the reasons for his decision:
Now let me give you the reasons for my decision.
A majority of the American people, a majority of you listening to me, are for the withdrawal of our forces from Vietnam. The action I have taken tonight is indispensable for the continuing success of that withdrawal program.
A majority of the American people want to end this war rather than to have it drag on interminably. The action I have taken tonight will serve that purpose.
A majority of the American people want to keep the casualties of our brave men in Vietnam at an absolute minimum. The action I take tonight is essential if we are to accomplish that goal.
We take this action not for the purpose of expanding the war into Cambodia but for the purpose of ending the war in Vietnam and winning the just peace we all desire. We have made–we will continue to make every possible effort to end this war through negotiation at the conference table rather than through more fighting on the battlefield.
Let us look again at the record. We have stopped the bombing of North Vietnam. We have cut air operations by over 20 percent. We have announced withdrawal of over 250,000 of our men. We have offered to withdraw all of our men if they will withdraw theirs. We have offered to negotiate all issues with only one condition–and that is that the future of South Vietnam be determined not by North Vietnam, and not by the United States, but by the people of South Vietnam themselves.
The answer of the enemy has been intransigence at the conference table, belligerence in Hanoi, massive military aggression in Laos and Cambodia, and stepped-up attacks in South Vietnam, designed to increase American casualties.
This attitude has become intolerable. We will not react to this threat to American lives merely by plaintive diplomatic protests. If we did, the credibility of the United States would be destroyed in every area of the world where only the power of the United States deters aggression.
Tonight, I again warn the North Vietnamese that if they continue to escalate the fighting when the United States is withdrawing its forces, I shall meet my responsibility as Commander in Chief of our Armed Forces to take the action I consider necessary to defend the security of our American men.
The action that I have announced tonight puts the leaders of North Vietnam on notice that we will be patient in working for peace; we will be conciliatory at the conference table, but we will not be humiliated. We will not be defeated. We will not allow American men by the thousands to be killed by an enemy from privileged sanctuaries.
The time came long ago to end this war through peaceful negotiations. We stand ready for those negotiations. We have made major efforts, many of which must remain secret. I say tonight: All the offers and approaches made previously remain on the conference table whenever Hanoi is ready to negotiate seriously.
But if the enemy response to our most conciliatory offers for peaceful negotiation continues to be to increase its attacks and humiliate and defeat us, we shall react accordingly.