The biggest drive in Russia’s and America’s in buildup of increasing amounts of intercontinental ballistic missiles was not the number of similar missiles the other side had. The goal was not to have more nuclear weapons than the enemy — the two sides, combined, had not only enough to eradicate every single structure over each other’s territory, but enough to do so over the entire world, several times over. Instead, the drive to increase nuclear arms was the enemy’s perceived missile defense capability. This was the major point of the Anti-Ballistic Missile Treaty.

On this day, August 3, in 1972, the ABM treaty was ratified, with both sides agreeing to reduce ABM deployments from two to one, deployed either around the capital of a missile launch site. The USSR deployed theirs around Moscow; the U.S. chose not to deploy one at all, and deactivated the one around a Minuteman ICBM launch area in Grand Forks, North Dakota.

The American decision to forego any ABM deployment may have come from the development by both sides of multiple-warhead missiles, called MIRVs (Multiple Independently Targetable Reentry Vehicles) that greatly reduced the power of ABMs. When a single missile could carry anywhere from 6-12 warheads, and some of them possibly decoys, an ABM interception system would quickly be overwhelmed.