The Nuclear Threshold Depends on Who—and Where

The lede

The Russia–Ukraine war fused the mud and mines of 1914 with the cheap drones and algorithms of 2025. Trenches, artillery duels, and miles‑deep minebelts were mapped in real time by quadcopters and loitering munitions, while both sides jammed each other’s radios and GPS. It’s a warning flare, not a template. A wider European war—or a direct fight between great powers—would start higher, move faster, and push harder into the air, space, and electromagnetic spectrum.

What Ukraine actually taught us

• Transparency and lethality. The ubiquity of drones plus precision fires made it hard to hide anything that moves or emits. Electronic warfare (EW) became a daily arms race; units adapted with fiber‑optic tethers, pre‑planned routes, and autonomous terminal guidance. Commercial space for comms and imagery became essential, and vulnerable.
• Industrial stamina matters. Ammunition and air‑defense production, not one‑off wonder weapons, shaped the campaign’s rhythm. The EU says it’s racing to lift capacity to ~2 million shells/year by end‑2025—a recognition that mass still wins.
• Drones are additive, not a substitute. Cheap FPVs changed tactics but didn’t erase the need for combined arms, air defense, and EW. Ukraine’s own drone chief warns NATO forces remain underprepared for a battlefield saturated with small UAS.

If the war spread in Europe, it wouldn’t look like 2022–25

Short answer: no. A NATO–Russia fight would open with salvo exchanges of cruise and ballistic missiles, suppression of integrated air defenses, and aggressive EW/cyber/space operations, not just positional trench warfare. Two big reasons:

1. Air and missile defense becomes the central nervous system. NATO has updated Integrated Air and Missile Defence (IAMD) policy and is layering systems from Patriot and SAMP/T to Germany’s new Arrow‑3 exo‑atmospheric interceptors under the European Sky Shield effort. Expect early strikes to focus on blinding and breaking these layers.
2. The “vertical” fight expands. Aegis Ashore in Poland is now live, and both sides would contest space services and spectrum from hour one, with knock‑on effects to navigation, comms, and battle networks.

Bottom line: Even where ground fronts harden into trenches, the decisive contest shifts upward—to the missile exchange, the air defense picture, and who keeps their networks alive.

Nuclear thresholds: it really does depend on who—and where

By the numbers (2025 best public estimates):

• France: ~290 warheads.
• United Kingdom: ~225 warheads today; policy cap raised to “no more than 260.”
• U.S. nuclear sharing in Europe: ~100 B61 bombs across six bases in five allied countries.
• Russia (non‑strategic/tactical weapons): ~1,558 warheads assigned to delivery systems (stockpile total ~4,380).
• China: ~500 warheads (Jan 2024) rising to ~600 (Jan 2025), with the Pentagon projecting >1,000 by 2030. Beijing maintains a formal No‑First‑Use pledge.

There’s no clock. Tactical nuclear use does not trip at Day 30 or Month 6. It hinges on leaders’ perceptions—regime survival, the fate of strategic forces and command networks, loss of vital territory, and misread signals. History shows nuclear‑armed crises that stayed conventional (e.g., Kargil 1999; Sino‑Soviet 1969), reinforcing a powerful “nuclear non‑use” norm. But Europe is uniquely “entangled”: multiple nuclear actors inside a tight battlespace. That raises risk.

Doctrine matters. U.S. policy confines any nuclear use to “extreme circumstances” to defend vital interests. Russia in 2024–25 revised guidance in ways analysts read as broadening contingencies, adding ambiguity about thresholds. China advertises No‑First‑Use, even as its arsenal grows. None of this “excludes” nuclear use in a great‑power war—but regions differ in risk.

Scenario 1: A wider European war (NATO–Russia)

Nuclear risk: elevated. Two European nuclear powers (France, UK), U.S. B61s forward‑deployed, and Russia’s large non‑strategic stock create dense escalatory linkages. Massive conventional strikes on air bases, IAMD nodes, and logistics hubs would sit under immediate nuclear shadow. Russia has even staged non‑strategic nuclear exercises near the theater.

How it starts: a salvo war—air and missile attacks, cyber/EW, and counter‑IAMD—before large‑unit ground action consolidates. Suppressing Russia’s layered IADS (Kaliningrad, Western Military District) is prerequisite to follow‑on airpower, and vice versa for NATO.

What endures from Ukraine: trenches, FPV drones, minefields. What changes: larger, smarter autonomous aircraft complement the cheap stuff; space support is hit harder; and industrial surge (munitions, interceptors) becomes the scoreboard.

Scenario 2: U.S.–Russia, directly

Nuclear risk: highest. Two heavily ready triads, dual‑capable systems, short decision timelines. Any side’s breakthrough that looks existential to the other could trigger nuclear signaling, alerts, or demonstrations. RAND’s (older) Baltics work is one reason NATO moved to forward defense and new regional defense plans—but the structural risk remains.

First week: reciprocal strikes on ISR/C2, air bases, long‑range fires; harsh counter‑space/EW. Escalation management is fragile because each side doubts the other will tolerate defeat in a high‑stakes theater.

Scenario 3: U.S.–China over Taiwan

Likely more conventional—at first. Expect a maritime‑air‑space‑cyber campaign inside thick A2/AD: long‑range precision strikes, anti‑ship ballistic missiles, massed air defense, under‑sea contests. China pledges No‑First‑Use; U.S. policy narrows nuclear use to extreme circumstances. But expert work and wargames show nuclear signaling is probable, and thresholds can blur if mainland targets are struck hard. So “excluded” is too strong.

Escalation management 101: Select targets that achieve denial without threatening regime survival; protect bomber and CCA basing against a Chinese “use‑or‑lose” reading; keep communication channels open even amid cyber/jamming. RAND’s framework is blunt: keeping a Taiwan fight under the nuclear threshold requires choices that trade speed for stability.

The autonomy pivot

The United States is pushing mass and intelligence into uncrewed systems:

• Replicator aims to field thousands of attritable autonomous systems across domains; $500 million/year was the opening budget line, with the first publicly named buy the Switchblade‑600.
• Collaborative Combat Aircraft (CCA) will team uncrewed “loyal wingmen” with fighters and bombers; RTX and Shield AI have been tapped to supply autonomy for Increment 1.

Case in point: Shield AI’s X‑BAT. Unveiled this week, X‑BAT is a jet‑powered, vertical takeoff/landing autonomous aircraft built around the company’s Hivemind AI:

• Range: “>2,000 nautical miles” (≈ 3,704 km).
• Ceiling: “>50,000 ft” (≈ 15.2 km).
• Concept: runway‑independent operations from ships, islands, austere sites; strike, counter‑air, EW, ISR; designed to “team” with manned aircraft in comms‑degraded, GPS‑jammed airspace.

It’s a glimpse of how next‑gen autonomy could reshape contested theaters: more launch points (VTOL), more persistence (range), and more collaborative tactics at machine speed. But survivability will still depend on signatures, IAMD density, and EW realities—not marketing lines about “penetrating any airspace.”

Read this as a warning, not a prophecy

Ukraine shows what happens when the factory, the fiber‑optic cable, and the quadcopter meet a 20th‑century front. A wider European war would be not just more of that, but more vertical and more electromagnetic—and closer to nuclear tripwires because of who is in the neighborhood. A U.S.–China clash is likelier to stay conventional longer, but it will be saturated with nuclear signaling as arsenals grow. The through‑line across all three: mass + autonomy + air/missile defense + industrial surge will shape outcomes—long before leaders face the worst decision of all.