President Nixon signs the SALT I (First Strategic Arms Limitation Treaty) with Soviet Premier Leonid Brezhnev on May 26, 1972 (Richard Nixon Presidential Library).

On April 21, 1972, National Security Advisor Henry Kissinger, and top aides Helmut Sonnenfeldt and Winston Lord met with Kremlin officials to talk the prospects of a scheduled Summit in Moscow. The diplomatic event had been on shaky ground since March 30, 1972, when the North Vietnamese launched an all out offensive on the South.

Five days before the April meeting, Nixon made the decision to bomb Hanoi, and mine the strategically important Haiphong Harbor, a central source of resupply for Communist forces. In the course of these strikes, U.S. bombers accidentally hit four Soviet merchant ships.

In a memo to Kissinger, Nixon weighed the risk of losing the Summit in Moscow:

Our desire to have the Soviet Summit, of course, enters into this, but you have prepared the way very well on that score, and in any event, we cannot let the Soviet Summit be the primary consideration in making this decision. As I told you on the phone this morning, I intend to cancel the Summit unless the situation military and diplomatically substantially improves by May 15 at the latest or unless we get a firm commitment from the Russians to announce a joint agreement at the summit to use our influence to end the war.

Soviet Premier Leonid Brezhnev complained to Kissinger, saying that there were “forces in the world which seek to bring about a heightening of tension.”

Despite reports to the contrary, they denied sending military aid to North Vietnam. They pointed their finger at China.

Nixon’s triangular diplomacy with China had in a short time created a new dynamic. Soviet leaders were worried, and eager for a Summit.

“It certainly would be quite a big gift to the Chinese if the meeting did not come off. It would only help China,” Brezhnev said.

The Summit went off as planned in May 1972, with major arms control treaties signed.

Read the whole memorandum of conversation between Dr. Kissinger and Soviet leaders below:

Memorandum of Conversation … by on Scribd