Following two and a half years of negotiations, President Richard Nixon and the Soviet Union's General Secretary Leonid Brezhnev on May 26, 1972, signed the Anti-Ballistic Missile Treaty causing ABM and Safeguard to become a major topic of discussion for the summer.

At that time, the mission for the Safeguard system was to protect the nation's land-based retaliatory forces against a direct attack from the Soviet Union; defend the American people against the kind of nuclear attack which the People's Republic of China might develop within the decade following the announcement; and provide protection against the possibility of accidental attacks from any source. Construction of the Safeguard sites in North Dakota and Montana were well underway and the next phase, development of a site in the National Capital Region, was under review.

This initial version of the ABM Treaty would limit both nations to two ABM sites -- one near its capital and the other near an intercontinental ballistic missile complex. The Soviet Union had deployed their ABM system around Moscow, while the American system was progressing in North Dakota and Montana near the MINUTEMAN fields of Grand Forks and Malmstrom Air Force Bases.

Each site was limited to 100 missiles and 100 launchers. An additional 15 launchers were allowed at test sites. Additional regulations stipulated the type and capabilities of the radars at the ABM sites.

Finally, the agreement prevented either nation from defending its entire territory. A separate interim accord, negotiated at the same time, set maximum limits for each country's intercontinental ballistic missiles and sea-launched ballistic missiles, to last for five years. This agreement, however did not limit the number of warheads per missile nor technological advances to improve offensive weapons.

Following the initial agreement, informal talks addressed the possibility of a third Safeguard deployment. The Joint Chiefs of Staff and the Nixon administration favored an ABM deployment to protect the nation's capital, providing the nation with the maximum protection allowed by the treaty.

Faced with congressional and popular opposition, however, "the administration quietly dropped its support of the Washington ring." Ultimately the appropriations packages, discussed on concurrent meetings, included no funding for a Washington site.

On July 21, following weeks of interviews and discussion, the Senate Foreign Relations Committee, headed by Sen. J.W. Fulbright, D-Arkansas, unanimously approved both agreements made by the president in May. With the support of key senators, the ABM Treaty moved to the full Senate with a goal of a final review and approval no later than mid-August, as negotiators hoped to renew their negotiations on weapons cuts in October.

The ABM Treaty came to a vote before full the Senate on Aug. 3, 1972. In a roll call vote, the Senate ratified the agreement by a vote of 88 to two, easily achieving the two-thirds margin needed to approve a treaty.

According to published reports, the two dissenters, Sen. James Buckley, Con-R, New York, and James B. Allen, D-Alabama, held that the agreement was "immoral because it causes the United States to forego an available means of defending its population against potential nuclear attack." Hailed by its supporters, however, the treaty was presented "as an historic first step on a journey toward ending the 'mad momentum' of the nuclear arms race."

Following a visit to the North Dakota Safeguard site in September, Deputy Secretary of Defense Kenneth Rush described the ABM system as a "catalyst" for the arms agreements. When questioned about the adequacy of the ABM system, Rush replied: "It's very impressive. … a magnificent engineering accomplishment." He later added that during the negotiations, it was the Russians who were most concerned about the defensive systems, while the Americans sought to address the offensive weapons.

The Soviet Union also ratified the treaty in August. The document was signed by President Richard Nixon signed on Oct. 3. The agreement was finalized with an exchange of instruments made on the same day.