Event Date: May 9, 1972

In early May 1972, as the U.S. Navy began to mine Haiphong harbor, President Richard Nixon appeared on television to address the nation. He opened his remarks as follows:

Five weeks ago, on Easter weekend, the Communist armies of North Vietnam launched a massive invasion of South Vietnam, an invasion that was made possible by tanks, artillery, and other advanced offensive weapons supplied to Hanoi by the Soviet Union and other Communist nations.

The bulk of foreign assistance for North Vietnam came from the USSR and the People's Republic of China, with about 60 percent of the total coming from the Soviet Union. China's initial share was substantial, but steadily diminished as Nixon's rapprochement with the PRC gained momentum. From 1965 through 1968 the overwhelming majority of assistance from the USSR was for the construction of an extensive North Vietnamese air defense system. Soviet military aid dropped off when the U.S. ceased bombing North Vietnam in November 1968, but it began to pick up sharply in 1971 and continued to increase steadily in 1972. Much of the new military assistance was in the form of armored fighting vehicles.

The 1972 Nguyen Hue Offensive

North Vietnam's Nguyen Hue Offensive, alternatively known as the Easter Offensive, was launched in an exclusively conventional mode; complete with tanks, sophisticated crew-served weapons and large attack formations. This giant step forward over the 1968 Tet Offensive was made possible by the provision of modern arms, for free, by the Union of Soviet Socialist Republics.

The Easter Offensive was the world's largest ground operation since the Korean War, when 300,000 Chinese soldiers crossed the Yalu River into North Korea. According to Vietnam's Ministry of National Defense, North Vietnam dedicated a force of about 10 battalions, equipped with 322 tanks and armored vehicles. Most of those tanks were either Soviet T-34 medium tanks of Second World War vintage, Soviet T-54 main battle tanks from the post-WWII era and Type 59s, which were Chinese-manufactured versions of the Soviet T-54A.

A 1969 U.S. National Security Study cited the Department of State as saying that about 85 percent of Communist aid to the Democratic Republic of Vietnam arrived by sea, with rail deliveries from China account for the remaining 15 percent. Most of those sea shipments arrived at the port of Haiphong, North Vietnam's only major seaport.

The Mining of Haiphong Harbor

By fielding a relatively modern army equipped with tanks, long-range artillery and air defense weapons, the People's Army of Vietnam had created a significant vulnerability for themselves. They were now heavily dependent on a large-scale, continuous supply of replacements, gasoline and ammunition. Interdiction of Haiphong harbor and rail lines from China would, over time, prevent Hanoi from receiving supplies required to continue the war effort.

In his televised address to the nation, Nixon continued:

All entrances to North Vietnamese ports will be mined to prevent access to these ports and North Vietnamese naval operations from these ports.

United States forces have been directed to take appropriate measures within the internal and claimed territorial waters of North Vietnam to interdict the delivery of any supplies.

Rail and all other communications will be cut off to the maximum extent possible. Air and naval strikes against military targets in North Vietnam will continue.

Until then, naval mining at Haiphong had often been a topic for consideration but it was always rejected, due to the risk of causing China or Russia to intervene. On May 9, 1972 (Vietnamese time), U.S. Navy A-7 Corsairs and A-6 Intruders from Carrier Task Force 77 of the Seventh Fleet began to sow mines at the entrance to Haiphong harbor and at other North Vietnamese seaports, in an operation code-named Pocket Money.

Coinciding with the President's address, a message was transmitted to forces in Southeast Asia to begin a bombing campaign code-named Operation Linebacker. Linebacker was designed to complete the crippling of North Vietnam's ability to conduct offensive operations in South Vietnam. The bombing aimed to destroy the North's petroleum storage facilities and power-generating plants and to impede the flow of soldiers and supplies by destroying transportation infrastructure. To complete the sealing off of North Vietnam from its outside suppliers, the campaign targeted railroads and highways connecting Vietnam with China.

Detente Proceeds Despite the Mining of Haiphong

President Lyndon Johnson had always refused advice from defense officials to mine North Vietnam's seaports. It was feared that this move could induce the Soviet Union to react strongly. The USSR might have simply decided to increase material support for Hanoi, or they just might have been motivated to intervene directly in Vietnam. The relaxation of tensions begun in Nixon's first term, together with Soviet eagerness to cool down the arms race, had created conditions more favorable for the mining of Haiphong.

Moscow and Beijing both denounced the U.S. action. Each one was unwilling to jeopardize their own thawing relations with the United States and was wary of their rival's dealings with America. Nixon's famous visit to China had only taken place towards the end of February of 1972; a little more than two months before Navy began the aerial mining of the harbor at Haiphong.

On May 22, only a couple of weeks after the mining of Haiphong harbor, a nine-day summit meeting began in Moscow between President Richard Nixon and General Secretary Leonid Brezhnev. That landmark summit meeting produced the signing of the Anti-Ballistic Missile Treaty, the first Strategic Arms Limitation Treaty, and a bilateral agreement called the U.S.–Soviet Incidents at Sea agreement.