---
title: "Nuclear Deterrence After New START: What It Is, How It Works, and What Changed in 2026"
description: "New START expired on February 5, 2026. What nuclear deterrence is, how it works, what was lost with the treaty, and why China changes the equation."
author: "Declan Farr"
category: "Tactics & Doctrine"
date: 2026-10-15T08:20:11.118Z
canonical: "https://defensebrief.co/blog/nuclear-deterrence-explained-after-new-start-expiry"
---

# Nuclear Deterrence After New START: What It Is, How It Works, and What Changed in 2026

![blocks, sprint, start](https://cdn.pixabay.com/photo/2019/07/14/22/15/blocks-4338240_1280.jpg?w=1200&q=75)

> New START expired on February 5, 2026. What nuclear deterrence is, how it works, what was lost with the treaty, and why China changes the equation.

For the first time since 1972, no treaty limits the strategic nuclear forces of the United States and Russia. New START expired on February 5, 2026. The weapons did not change overnight, but the rules, the inspections and the shared data that surrounded them are gone. That makes this the right time to ask what nuclear deterrence actually is, and what it needs to work.

This briefing defines the doctrine, explains the mechanism, and then sets out what changed in 2026. Where a claim is an estimate or a forecast, we say so.

## What Nuclear Deterrence Means

  ![](https://cdn.pixabay.com/photo/2019/10/06/06/56/nuclear-power-plant-4529392_1280.jpg?w=960&q=75)
  Photo by [distelAPPArath](https://pixabay.com/photos/nuclear-power-plant-cooling-tower-4529392/) on [Pixabay](https://pixabay.com)

Nuclear deterrence is the use of the threat of nuclear retaliation to persuade an adversary not to take an action, most often not to attack. It is a psychological relationship backed by hardware. The adversary must believe three things: that you have the capability to retaliate, that you have the will to do so, and that you can communicate the threat clearly.

Two forms matter. Deterrence by punishment threatens a cost so high that no gain could justify the attack. Deterrence by denial aims to make the attack fail. Nuclear forces serve the first form almost entirely, which is why survivability, meaning the ability to ride out a first strike and still respond, is the technical heart of the doctrine.

## Why It Developed

  ![](https://cdn.pixabay.com/photo/2019/10/08/18/41/nuclear-power-plant-4535760_1280.jpg?w=960&q=75)
  Photo by [distelAPPArath](https://pixabay.com/photos/nuclear-power-plant-rhine-flow-4535760/) on [Pixabay](https://pixabay.com)

The doctrine grew out of the late 1940s and 1950s, when the Soviet Union ended the American nuclear monopoly. Strategists concluded that when both sides can destroy the other even after being hit first, a first strike cannot be rational. This is the logic usually called mutual assured destruction. It rests on the survivable forces of both sides: land-based missiles in hardened silos, submarines at sea and bombers.

Arms control then grew up around deterrence, not against it. Treaties capped numbers, banned some systems and, crucially, built transparency, so that neither side had to assume the worst about the other.

## How It Works in Practice

  ![](https://cdn.pixabay.com/photo/2018/10/25/19/36/soap-3773185_1280.jpg?w=960&q=75)
  Photo by [noah1974](https://pixabay.com/photos/soap-baba-what-do-you-mean-3773185/) on [Pixabay](https://pixabay.com)

Deterrence runs on signalling and on uncertainty. States publish declaratory policies about when they would consider using nuclear weapons. They exercise forces, test missiles and move submarines and bombers to show capability. They also keep real doubt in the adversary's mind about the exact threshold.

The Council on Foreign Relations summarised what New START had capped: 1,550 deployed warheads, 700 deployed ballistic missiles and bombers, and 800 strategic launchers for each country. Inspections stopped during the pandemic and never resumed, and Russia suspended its participation in 2023, but the numerical limits and the data exchange framework stayed on the books until the end date.

## What Changed in February 2026

According to a [February 2026 analysis by Erin Dumbacher at the CFR](https://www.cfr.org/articles/nukes-without-limits-a-new-era-after-the-end-of-new-start), the expiry removes several things: on-site inspections, routine data exchange, the Bilateral Consultative Commission that handled disputes, and mutual commitments not to interfere with each other's satellites and other national technical means of intelligence.

The loss of those last two items is easy to overlook. Satellites are how each side verifies the other without trust. Take away the formal pledge not to interfere and the system depends on restraint instead of text.

On the political side, the picture is mixed and still moving. Reporting in February, including a scoop from Axios, described an informal understanding that both sides would keep observing the treaty's central limits for a time without a legal extension. The Vienna Center for Disarmament and Non-Proliferation, writing later, said no bilateral or multilateral negotiations were under way or planned. We could not find a confirmed replacement agreement as of this writing, so readers should check current reporting.

> 
"I do not believe arms control is dead. It remains a useful tool."

- Jane Vaynman, Johns Hopkins SAIS and former State Department senior adviser, quoted by the [Council on Foreign Relations](https://www.cfr.org/articles/nukes-without-limits-a-new-era-after-the-end-of-new-start)

## Strengths and Weaknesses of the Doctrine

Deterrence has a strong claim in its favor: the nuclear powers have not fought a direct war with each other since 1945. It is hard to prove cause and effect, and deterrence skeptics note that luck and crisis management may have mattered as much as doctrine.

Its weaknesses are structural.

- It depends on rational calculation under stress, and crises compress time and information.

- It is vulnerable to misperception, because each side reads the other's capabilities and intent through imperfect data.

- It becomes harder with three major powers instead of two. Planning against two peers at once is a different problem from a bilateral balance.

## The Third Player: China

The Stockholm International Peace Research Institute (SIPRI) estimates in its 2026 Yearbook that China held about 620 warheads in January 2026, up from 600 a year earlier, as [reported by the South China Morning Post](https://www.scmp.com/news/china/military/article/3356269/china-adds-warheads-nuclear-powers-walk-away-disarmament-sipri). These are estimates, since China does not publish its inventory. The CFR piece, citing SIPRI, notes projections that Chinese forces could approach parity with American forces by 2035. Treat that as a forecast.

The strategic issue is not the exact count but the structure. A bilateral treaty cannot bind a third party, and Washington and Moscow both have reasons to want Beijing in any future framework. Beijing has so far shown little interest in joining one.

## What Adversaries Get Right or Wrong

A common error among commentators is to treat nuclear deterrence as a numbers contest. Past a point, extra warheads add little to the threat of retaliation. What matters more is whether forces survive and whether the other side believes you would respond. Another error is to assume that lower numbers mean lower risk. Fewer weapons that are easier to target can be less stable than more weapons that are hard to destroy.

A related debate concerns smaller, regional nuclear relationships and security guarantees. Our piece on the [Saudi-Pakistan defence treaty](/saudi-pakistan-treaty-nuclear-implications) looks at how extended deterrence claims travel beyond the original superpower pairing.

## Future Relevance

Three questions will define the next phase. Will Washington and Moscow formalise their informal restraint? Will any process include China? And will the loss of inspections and data exchange erode confidence faster than the arsenals change? None has a settled answer. The CFR also cites former U.S. negotiator Rose Gottemoeller on one near-term priority: getting constraints on nonstrategic nuclear warheads.

It is also worth remembering that deterrence is not limited to nuclear weapons. Our explainer on [military doctrine](/military-doctrine-explained-why-strategy-shapes-outcomes) shows how conventional and nuclear postures interact.

## Final Assessment

Nuclear deterrence has survived the loss of treaty limits before, and it may do so again. But it was built to run alongside transparency, and that is the part now in short supply. The question for 2026 is not whether deterrence still works in principle. It is whether it works as well when each side must guess at the other's forces rather than count them.

## FAQs about nuclear deterrence

### What is nuclear deterrence?

It is the threat of nuclear retaliation used to discourage an adversary from attacking. It depends on capability, will and clear communication of the threat.

### When did New START expire?

On February 5, 2026. No binding limit on U.S. and Russian strategic nuclear forces remains in force.

### What did New START limit?

According to the CFR, 1,550 deployed warheads, 700 deployed ballistic missiles and bombers, and 800 strategic launchers for each country.

### How many warheads does China have?

SIPRI estimated about 620 in January 2026. China does not publish figures, so this is an outside estimate.

## FAQ

### What is nuclear deterrence?

The threat of nuclear retaliation used to discourage an attack. It needs capability, will and clear communication.

### When did New START expire?

On February 5, 2026. No binding limit on U.S. and Russian strategic forces remains.

### What did New START limit?

Per the CFR: 1,550 deployed warheads, 700 deployed missiles and bombers, and 800 launchers for each country.

### How many warheads does China have?

SIPRI estimated about 620 in January 2026. China publishes no figures, so this is an outside estimate.


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Source: https://defensebrief.co/blog/nuclear-deterrence-explained-after-new-start-expiry