US and Russian strategic arsenals lose agreed numerical limits

September 26 is the UN International Day for the Total Elimination of Nuclear Weapons. The UN says New START expired on February 5, 2026 without a successor, leaving US and Russian strategic nuclear arsenals without bilaterally agreed numerical limits for the first time since the 1970s. Secretary-General António Guterres says the threat of nuclear catastrophe is growing as tensions, mistrust, military competition and arsenal modernization intensify. The observance is not a new treaty or a disarmament result; the real measures are whether negotiations, verification and enforceable numerical limits return.