Flowers placed during a vigil for the 79th anniversary of the bombing of Hiroshima and Nagasaki. Photo: Jon Krieg/AFSC
The world changed forever in August 1945, when the United States dropped atomic bombs on Hiroshima and Nagasaki, killing an estimated 110,000 to 210,000 people. Scientists, activists, policymakers, and peacebuilders—including organizers at AFSC—have spent the decades since calling for disarmament and an end to all nuclear threats. One crucial result of that work was arms control treaties that limited nuclear arsenals.
But now, that work is being unraveled. On Feb. 5, 2026, the last remaining U.S.-Russia nuclear arms reduction treaty, expired. The New Strategic Arms Reduction Treaty (New START) had placed limits on deployed nuclear weapons and created channels for inspections and monitoring.
With the end of the treaty, the guardrails that create transparency and prevent a nuclear arms race end.
Here is what you need to know:
1. The U.S. and Russia hold nearly all the world’s nuclear weapons.
The United States and Russia together possess almost 90% of the world’s nuclear weapons. That is why New START matters even to people far from Washington and Moscow. A world with no limits on the two largest nuclear stockpiles is a more dangerous world.
Without New START, there would be no legally binding guardrails on the two countries’ long-range nuclear weapons for the first time since the first U.S.-Soviet arms control agreements in the early 1970s.
And the risk is not only long-term nuclear development. Without limits, either side could increase the number of nuclear weapons ready to launch relatively quickly by “uploading” additional warheads onto existing missiles, which can fuel pressure for the other side to respond.
2. Arms control makes everyone safer.
New START capped the U.S. and Russia at 1,550 deployed nuclear weapons and limited deployed delivery systems, with an overall limit on launchers and bombers. Those numbers are more than technical details. They limit how many weapons can be used quickly in a crisis.
New START also helped reduce nuclear risks in practical ways:
- It increased transparency and predictability through notifications, data exchanges, and inspections.
- It reduced worst-case assumptions that can fuel an arms race. When transparency collapses, nuclear-armed states opt for worst-case thinking, and that increases pressure to build more weapons and signal more aggressively.
At its best, arms control lowers the risk that misunderstanding becomes escalation.
3. Russia offered to continue the New START limits, but the U.S. has not accepted.
Russian officials have said they are prepared to continue New START’s limits for one year after expiration, if the U.S. acts in a similar spirit. The U.S. has not responded.
President Donald Trump has said he wants a “better” agreement and has expressed interest in involving China. But making China a precondition risks losing current guardrails on the two largest weapons stockpiles. Beijing has resisted joining nuclear arms control agreements because its weapons stockpile is smaller than the U.S. and Russia. It has argued that the countries with the two largest stockpiles have a responsibility to reduce their stockpiles first.
The urgent priority is to preserve existing constraints and transparency between the United States and Russia, then build additional risk-reduction steps with China and other nuclear-armed states.
4. This moment should push the U.S. to expand risk reduction, not abandon it.
The most immediate step is to stop a new unconstrained U.S.-Russia arms race. But this moment can also be a turning point.
A safer path forward includes rebuilding U.S.-Russia transparency and limits, while pursuing practical risk-reduction measures with other nuclear-armed states. Nuclear risks are growing as expansion continues across all nine nuclear-armed countries.
The only world truly safe from nuclear war is a world free of nuclear weapons. Until then, every verifiable limit, every inspection, and every channel for communication is part of protecting human life.
Take action: Urge Congress to prevent a new nuclear arms race.
You can join advocates across the country urging Congress to actively pursue a world free of nuclear weapons. Contact your representative and encourage them to co-sponsor H.Res. 317, which calls on the United States to lead the world back from the brink of nuclear war and halt and reverse the nuclear arms race.
