On April 30th 1970, president Richard Nixon appeared on television and told Americans that he had authorised the deployment of United States troops and aircraft against suspected communist positions in Cambodia:

“Good evening my fellow Americans.

Ten days ago, in my report to the nation on Vietnam, I announced a decision to withdraw an additional 150,000 Americans from Vietnam over the next year. I said then that I was making that decision despite our concern over increased enemy activity in Laos, Cambodia, and in South Vietnam.

At that time, I warned that if I concluded that increased enemy activity in any fo these areas endangered lives of Americans remaining in Vietnam, I would not hesitate to take strong and effective measures. Despite that warning, North Vietnam has increased its military aggression in all these areas, and particularly in Cambodia.

After full consultation with the National Security Council, Ambassador Bunker, General Abrams, and my other advisors, I have concluded that the actions of the enemy in the last 10 days clearly endanger the lives of Americans who are in Vietnam now and would constitute an unacceptable risk to those who will be there after withdrawal of another 150,000.

To protect our men who are in Vietnam and to guarantee the continued success of our withdrawal and Vietnamization programs, I have concluded that the time has come for action. Tonight, I shall describe the actions of the enemy, the actions I have ordered to deal with that situation, and the reasons for my decision.

Cambodia, a small country of seven million people, has been a neutral nation since the Geneva agreement of 1954 an agreement, incidentally, which was signed by the Government of North Vietnam. American policy since then has been to scrupulously respect the neutrality of the Cambodian people. We have maintained a skeleton diplomatic mission of fewer than 15 in Cambodia’s capital, and that only since last August. For the previous 4 years, from 1965 to 1969, we did not have any diplomatic mission whatever in Cambodia. And for the past 5 years, we have provided no military assistance whatever and no economic assistance to Cambodia.

North Vietnam, however, has not respected that neutrality. For the past five years, as indicated on this map that you see here, North Vietnam has occupied military sanctuaries all along the Cambodian frontier with South Vietnam. Some of these extend up to 20 miles into Cambodia…

In cooperation with the armed forces of South Vietnam, attacks are being launched this week to clean out major enemy sanctuaries on the Cambodian Vietnam border. A major responsibility for the ground operations is being assumed by South Vietnamese forces… There is one area, however, immediately above Parrot’s Beak, where I have concluded that a combined American and South Vietnamese operation is necessary.

Tonight, American and South Vietnamese units will attack the headquarters for the entire communist military operation in South Vietnam. This key control centre has been occupied by the North Vietnamese and Viet Cong for five 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…

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…

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…

My fellow Americans, we live in an age of anarchy, both abroad and at home. We see mindless attacks on all the great institutions which have been created by free civilisations in the last 500 years. Even here in the United States, great universities are being systematically destroyed… If, when the chips are down, the world’s most powerful nation, the United States of America, acts like a pitiful, helpless giant, the forces of totalitarianism and anarchy will threaten free nations and free institutions throughout the world.”