Feb 2010 – The United States and Russia sign the New START treaty, capping each side at 1,550 deployed strategic warheads and 700 delivery systems and establishing the last bilateral nuclear arms‑control framework of the post‑Cold War era [1][14].

Feb 2011 – New START enters into force, instituting on‑site inspections, data exchanges and a verification regime that limits the two largest nuclear arsenals for the first time since SALT II [1][11].

2021 – The treaty receives a five‑year extension, pushing its expiry to 5 Feb 2026 and creating a deadline for future negotiations [1][11].

2022 – A Pentagon report projects China’s nuclear stockpile could reach about 1,500 warheads by 2035, underscoring the treaty’s omission of Beijing and prompting calls for a China‑inclusive pact [1].

2023 – Russia suspends participation in New START verification, accusing the United States of “strategic defeat” and citing inspection disputes, while the United States withholds data in response [11][6].

Jan 2025 – Donald Trump returns to the White House, reiterating his 2018 withdrawal from the Iran nuclear deal and signaling a hard‑line stance on arms‑control treaties [14].

Sep 22 2025 – President Vladimir Putin offers a voluntary one‑year extension of New START limits, but the United States gives no official reply, leading Russian officials to label the silence “erroneous and regrettable” [6][9].

Feb 4 2026 – Russia’s foreign ministry warns it is ready to take “decisive action” once New START lapses, asserting that the two powers will be free from treaty obligations [6].

Feb 5 2026 – New START formally expires, ending the last legally binding caps on U.S. and Russian strategic nuclear arsenals for the first time in over 50 years [1][11][13].

Feb 5 2026 – President Donald Trump posts on Truth Social that the United States will not extend New START, calling it “badly negotiated” and urging nuclear experts to draft a “new, improved, and modernized” treaty that includes China [1][4][5].

Feb 5 2026 – Secretary of State Marco Rubio states the administration will not maintain the existing caps and insists any future agreement must involve China to reflect 21st‑century realities [1][4].

Feb 5 2026 – The Russian foreign ministry declares the lapse “erroneous and regrettable” for the U.S. but says Russia is now free to act without treaty constraints, hinting at possible “decisive steps” [1][6][10].

Feb 5 2026 – Former New START chief negotiator Rose Gottemoeller warns the expiration benefits Putin and harms the United States’ image, calling it a diplomatic win for Moscow [5].

Feb 5 2026 – Former Russian President Dmitry Medvedev warns the treaty’s expiry could accelerate the Doomsday Clock, urging global attention to heightened existential risk [2][5].

Feb 5 2026 – The Bulletin of the Atomic Scientists moves the Doomsday Clock to 85 seconds to midnight (later reported as 89 seconds), citing the treaty’s lapse and rising nuclear danger as the closest setting ever [3][7].

Feb 5 2026 – Arms‑control experts Paul Dean, Matthew Kroenig and others warn that abandoning the limits could spark a three‑way U.S.–Russia–China arms race, eroding strategic stability [1][7].

Feb 5 2026 – The Kremlin publicly calls the expiration “negative,” expresses regret, and pledges a “responsible, thorough approach to stability” while inviting dialogue if constructive responses arise [10].

Feb 5 2026 – Senior U.S. and Russian officials meet in Abu Dhabi and agree to resume high‑level military‑to‑military dialogue, reopening a channel suspended in 2021 despite the treaty’s end [10].

Feb 7‑8 2026 – New York Times reporters David Sanger and William Broad warn that a “new generation of nuclear weapons” emerges as “vengeance after New START,” signaling a fresh arms competition [13].

Feb 23 2026 – Deputy Secretary of State for Arms Control Christopher Yeaw tells the Geneva disarmament conference that China is rapidly expanding its nuclear arsenal, could field over 1,000 warheads by 2030 and may achieve parity with the United States within four to five years, accusing Beijing of “deliberately and without constraint” development [12].

2026 onward – The Trump administration signals intent to craft a China‑inclusive nuclear treaty, revives “Trump‑class” battleship concepts and pursues AI‑driven weapons programs that blur nuclear and conventional lines, while NATO acquires Palantir’s AI battle‑management system, indicating a shift toward multilateral and technological competition [3][4][14].