Tactical nuclear weapons and electromagnetic pulse (EMP)

The phrase 'tactical nuclear weapon' is looser than it sounds. No treaty defines it. It is generally applied to lower-yield, shorter-range nuclear weapons intended for use on a battlefield or within a single theatre, as opposed to strategic weapons aimed at targets in an adversary's homeland. The boundary is political and doctrinal rather than physical: the same warhead can count as tactical or strategic depending on how it is deployed.

This article gathers what specialist public sources — SIPRI, the Federation of American Scientists, US Congressional Research Service reports — record about these weapons and about nuclear electromagnetic pulse. It is descriptive throughout: no design data, no employment parameters, nothing that would serve as operational guidance.

What makes a weapon non-strategic

Specialists prefer the term 'non-strategic', because it avoids endorsing the notion that a nuclear detonation can be a local, manageable event. The usual features are lower yield, short- and medium-range delivery systems — artillery, theatre missiles, gravity bombs — and, above all, a far weaker verification regime: no treaty in force limits or counts these arsenals, unlike deployed strategic warheads.

That absence of accounting is why every available figure is an estimate. Inventories in the SIPRI Yearbook and the FAS Nuclear Notebook credit Russia with the largest non-strategic arsenal, on the order of one to two thousand stored warheads, and the United States with a much smaller set: roughly a hundred B61 gravity bombs deployed at European bases under NATO nuclear sharing, plus low-yield warheads carried at sea. These are analysts' estimates, not official data.

Why analysts are concerned

The academic debate turns less on yield than on threshold. The most common criticism is that an arsenal of low-yield weapons makes first use more thinkable, and that no actor can guarantee a limited nuclear detonation will not trigger a larger response. Verification compounds the problem: because these warheads are not counted, reductions cannot be checked and confidence cannot be built around them.

The legal instrument that came closest to addressing this was the 1987 INF Treaty, which eliminated American and Soviet ground-launched intermediate-range missiles. The United States withdrew in 2019, citing Russian non-compliance, and with that the only agreement restricting an entire class of theatre delivery systems lapsed.

What nuclear electromagnetic pulse is

A high-altitude nuclear detonation generates a powerful electromagnetic pulse that can induce damaging currents in power grids and electronic equipment across very large areas, without thermal or blast effects at ground level. Technical literature describes the phenomenon in three successive components, known as E1, E2 and E3, which act on different timescales and affect fast electronics, lightning-protection-type systems, and long transmission lines and transformers respectively.

The empirical evidence comes from the atmospheric tests of 1962, before the moratorium. In the American Starfish Prime test, a detonation about 400 kilometres above the Pacific caused streetlight and telephone-circuit failures in Hawaii, more than 1,300 kilometres away, and damaged several satellites over the following weeks through radiation trapped in the Earth's magnetic field. Soviet tests that same year over Kazakhstan caused documented damage to power lines and a generating station.

How large the risk is today is disputed. The US commission set up to study EMP concluded in its reports that such an attack could cause prolonged damage to critical infrastructure; other specialists argue those conclusions overstate the effect on modern grids and understate repair capacity. It is an open technical debate and should be presented as one, not as settled fact.

• There is no legal definition of a 'tactical nuclear weapon': it is a doctrinal label.
• No treaty in force counts or limits non-strategic arsenals.
• All public figures are estimates produced by specialist institutes.
• Nuclear EMP is known mainly from the atmospheric tests of 1962.
• The scale of damage an EMP attack would cause today remains technically contested.