The US and Soviet Union negotiated and signed an agreement that limited nuclear tests to no more than 150 kilotons of explosive power—roughly 10 times the size of the Hiroshima blast. This limit was seen as a way to “stabilize” the nuclear balance and prevent one side from gaining advantage. Signed in 1976, the treaty was not ratified and entered into force until 1990. This delay was due both to geopolitical factors and to a lack of confidence in the ability to measure test size. By 1987, treaty compliance could be assured by several methods, including hydrodynamic tests, seismic monitors, and direct on-site inspection. LEARN MORE
Throughout the ‘70s the Cold War rivalry between the US and Soviet Union continued. But a rise in non-nuclear conflicts and tensions around the world—from the Vietnam War and the energy crisis to Middle East conflicts and the Soviet invasion of Afghanistan—led to new arrangements designed to keep the nuclear “balance of terror” in check. While weapons innovation continued, so too did innovation in risk reduction and the building of political will.
Early efforts by the US and Soviet Union to design and build missile defense systems were stymied by the realization that such systems would likely compel both sides to build more weapons in order to overwhelm the other’s defenses. The ABM Treaty, entered into force in 1972, allowed the US and USSR to have two ABM sites each: one protecting their capital, and another protecting a weapons site. The treaty’s innovations were mostly political but also technical: satellite verification was a key component, and the treaty was the first to prohibit countries from interfering with one another’s verification tools. LEARN MORE