- Hybrid attacks
- Hostile acts that stop short of open war and are easy to deny: cyber attacks, sabotage, cut undersea cables, drones over bases, spying and lies spread online.
- Proxies
- People or groups who act for a state so it can deny being involved, often criminals hired online.
- Attribution
- A government officially naming who was behind an attack. For sabotage and cyber attacks it can take months.
- The betting crowd, the forecasting crowds
- Polymarket is a website where people bet real money on whether something will happen; the price works as the crowd's odds (10% means about a 1-in-10 chance). Good Judgment Open and Metaculus are sites where many people forecast and are scored on accuracy. We use them only as a cross-check.
- A limited test
- A small, fast Russian move against a NATO member, such as seizing a border town, meant to show that NATO will not fight for it. Not an invasion.
- The Baltic clock
- Baltic officials' estimate that Russia could be ready for a limited move 2-3 years after the war in Ukraine ends. A ceasefire would start it.
- Readiness, the readiness deadline
- Readiness is how prepared forces are to fight at short notice. The readiness deadline is the date by which Britain aims to be ready to fight alongside its allies if it had to. Not a date when war is expected.
- % of GDP
- Spending measured against everything the economy produces in a year. 3% of GDP on defence is about 3p in every £1.
- Deterrence
- Preventing an attack by making the attacker expect it to cost more than it gains. A nuclear deterrent does this with the threat of a nuclear reply.
- Article 5
- NATO's promise that an armed attack on one member is an attack on all; each member then decides how to help. Used once, after 11 September 2001.
- Battlegroup
- A multinational force of one to a few thousand troops that NATO keeps in its eastern members, so that an attack on one would involve many allies at once.
- Brigade
- An army formation of several thousand troops.
- JEF (the Joint Expeditionary Force)
- A group of ten northern European countries, led by Britain, that can act together quickly: the UK, the Nordic and Baltic states, and the Netherlands.
- Kaliningrad
- A piece of Russia on the Baltic coast between Poland and Lithuania, cut off from the rest of Russia. Home to Russia's Baltic Fleet.
- Shadow fleet
- Old tankers with murky owners and insurance that Russia uses to sell oil despite sanctions.
- Escorts
- Russian warships sailing with shadow-fleet tankers, which would make stopping a tanker far riskier.
- GRU
- Russia's military intelligence service, blamed for sabotage and assassination plots in Europe, including the Salisbury poisoning in 2018.
- Détente
- An easing of tension between rivals.
- Arms control, New START
- Treaties that cap and inspect nuclear weapons. New START, the last one between the US and Russia, lapsed on 5 Feb 2026.
- Nuclear doctrine
- A country's stated rules for when it would use nuclear weapons.
- Alert levels
- How ready nuclear forces are to launch. Raising them is a warning sign.
- Nuclear sharing
- NATO's arrangement in which allied jets and crews train to carry American nuclear bombs kept in Europe.
- Battlefield nuclear use
- A smaller nuclear weapon used against troops in a war zone, or as a one-off warning, rather than on cities.
- Mobilisation
- Calling up reserves and putting a country's forces and industry on a war footing.
- Recall, the Strategic Reserve
- Calling former service personnel back to duty. The Strategic Reserve is that pool, about 95,000 people. It never covers anyone who has not served.
- Conscription, the draft
- Making people serve in the forces by law. Britain's last call-ups were in 1960.
- The price cap
- The most energy suppliers can charge households on standard tariffs, set by Ofgem every three months. The headline figure is a typical household's bill for a year.
- The bond market
- Where the government borrows. If lenders lose confidence, borrowing gets dearer, which limits how much more it can spend, on defence or anything else.
- Storm Shadow
- A long-range British-French cruise missile, supplied to Ukraine since 2023.
- Patriot
- An American air and missile defence system.
- Valdai
- A yearly forum in Russia where Putin speaks at length. The 2026 one was on 1 Oct.
- Red team
- Arguing hard against our own judgements to find their weak spots. Where one did not survive, we changed it.