Research conducted by Perplexity AI using the following sources:

• New START at a Glance | Arms Control Association
• Statement by the Secretary-General on the occasion of the expiration of the Treaty on Measures for the Further Reduction and Limitation of Strategic Offensive Arms (New START)
• New START expiration: what it means and what's next - ICAN
• Statement On the Expiration of the Last Treaty Restricting the World's Two Largest Nuclear Arsenals — New START
• After New START expires, Europe needs to step up on arms control
• The New START Treaty Is Ending. What Does That Mean for Nuclear Risk?