Nine nuclear arsenals, nine decisions to modernize.
Arms control weakens when strategic rivals treat increasingly capable weapons as a permanent answer.
Bad outcome probability
At least five of the nine nuclear-armed states will actively pursue arsenal modernization in 2027.
A nuclear weapon is not safer simply because it is newer. Each replacement system can be justified as a deterrent, but aggregate modernization may also intensify insecurity.
SIPRI’s research identifies modernization across nuclear-armed states. That observed activity is distinct from claiming that an actual nuclear attack is imminent.
The danger is structural: competing systems can magnify mistrust when arms-control rules and the institutions needed to verify them erode.
What this could mean.
- Why this could be bad
- Modernized nuclear forces may deepen arms races, while errors or escalatory miscalculation can create catastrophic danger.
- Possible repercussions
Governments could divert public resources into increasingly expensive weapons systems.
Shorter decision windows may increase the risks of mistakes in a crisis.
The consequences of nuclear use would extend far beyond the states involved.
The assessment.
- What we are forecasting
- At least five of the nine nuclear-armed states will actively pursue arsenal modernization in 2027.
- Time horizon
- Through December 2027
- Editorial confidence in the evidence: 95%
- SIPRI documented modernization among all nine nuclear-armed states in its reporting on 2025.
- What could change the outcome
- New negotiations, spending changes or verification agreements could curb particular programmes.
The evidence.
- SIPRI Yearbook 2026 ↗Stockholm International Peace Research Institute · 2026