New START

New START was a nuclear arms reductiontreaty between the United States and Russia with the formal name of Measures for the Further Reduction and Limitation of Strategic Offensive Arms. It was signed on 8 April 2010 in Prague, and after ratification it entered into force on 5 February 2011.

New START replaced the Treaty of Moscow (SORT), which was to expire in December 2012. It followed the START I treaty, which expired in December 2009; the proposed START II treaty which never entered into force; and the START III treaty, for which negotiations were never concluded.

The treaty called for halving the number of strategic nuclear missile launchers. It also called for the establishment of a new inspection and verification regime, replacing the SORT mechanism. It did not limit the number of operationally inactive nuclear warheads that can be stockpiled.

On 21 February 2023, Russia suspended its participation in New START. However, it did not withdraw from the treaty, and clarified that it would continue to abide by the numerical limits in the treaty. On 5 February 2026, the treaty officially expired.