THE TREATY was signed in Moscow on May 26, 1972, by US President Richard Nixon and Soviet leader Leonid Brezhnev. It is a cornerstone of international arms control agreements reached during the Cold War nuclear faceoff between the Soviet Union and the United States.

The relatively short treaty, which fits onto five sheets of paper, has 16 articles. After ratification, it entered into force on Oct 3, 1972.

Article XV gave each side the opportunity to withdraw with a six-month notice period if it considered the treaty “jeopardized its supreme interests”.

The accord restricts the deployment of ABM defenses by either side to a single system, with a highly limited scope, at a single designated site. It also strictly limits testing of new systems. ABMs were deemed to include interceptor missiles, launchers and associated radar systems.

BASIS OF TREATY: Setting out the basis of the treaty, the introduction stated: “Proceeding from the premise that the limitation of anti-ballistic missile systems, as well as certain agreed measures with respect to the limitation of strategic offensive arms, would contribute to the creation of more favourable conditions for further negotiations on limiting strategic arms...”

WHAT IS ALLOWED: Each party was originally permitted to have one limited ABM to protect its capital and a further one to protect an Intercontinental Ballistic Missile (ICBM) launch area. In 1974, the United States and the Soviet Union signed a protocol reducing the number of deployment areas to one.

At each site there may be no more than 100 ABM launchers and 100 ABM interceptor missiles with an operating radius of no more than 93 miles (150 km).