How did the Strategic Defense Initiative challenge détente?

The Strategic Defense Initiative (SDI) challenged détente by escalating the arms race and increasing tensions between the US and USSR.

The Strategic Defense Initiative, announced by US President Ronald Reagan in 1983, was a proposed missile defence system intended to protect the United States from attack by ballistic strategic nuclear weapons. This initiative marked a significant shift in the US's approach to the Cold War, moving away from the policy of détente that had been pursued in the 1970s. Détente, a French term meaning 'relaxation', referred to the easing of strained relations, especially in a political situation. In the context of the Cold War, it was characterised by a reduction in tensions and a slowdown in the arms race between the US and USSR.

The SDI, however, represented a return to a more confrontational stance. It was seen as a direct challenge to the USSR's military capabilities, as it threatened to undermine the balance of power that had been maintained through the policy of mutually assured destruction (MAD). MAD was based on the idea that neither side would start a nuclear war because they knew the other could retaliate with equal force, leading to their own destruction. By developing a system that could potentially intercept and destroy incoming missiles, the US was effectively seeking to neutralise the USSR's nuclear deterrent.

Furthermore, the SDI was perceived by the Soviets as a violation of the Anti-Ballistic Missile (ABM) Treaty of 1972, which was a key component of détente. The treaty limited the number of ABM systems each side could have, in order to maintain the balance of power. The SDI was seen as an attempt to circumvent these restrictions, leading to accusations of bad faith and increasing mistrust between the two superpowers.

The announcement of the SDI also led to an escalation in the arms race, as the USSR felt compelled to develop its own countermeasures. This put additional strain on the Soviet economy, which was already struggling due to the costs of maintaining parity with the US in terms of conventional and nuclear forces. The increased tensions and competition caused by the SDI thus served to undermine the principles of détente, leading to a renewed period of Cold War hostility.