War exclusion

Category: Policy exclusions · Reviewed by the Apex broking team · Last reviewed 2026-08-22 · ~5 min read

What the exclusion does

Conventional UK property, liability and package wordings exclude loss, damage, liability or expense directly or indirectly caused by, resulting from or in connection with war, whether declared or not, invasion, acts of foreign enemies, hostilities, civil war, rebellion, revolution, insurrection, military or usurped power. The exclusion is usually drafted with “directly or indirectly” and “in connection with” language, which is deliberately wider than proximate cause and is intended to catch consequential and remote effects as well as immediate ones.

Why war is excluded rather than priced

Insurance works on the aggregation of independent risks. War produces simultaneous, correlated losses across an entire portfolio, of unknown magnitude, with no reliable frequency data and no meaningful reinsurance capacity behind it. The exclusion is therefore structural. Where war-type risks are insured at all, they are written as a specialist class in dedicated markets with their own wordings, aggregate limits and cancellation provisions — typically with a short notice of cancellation clause allowing cover to be withdrawn as a situation deteriorates.

The terrorism boundary

Terrorism is treated separately from war, and the line between them is a drafting question rather than a factual one. Standard UK commercial property wordings exclude terrorism as well as war; terrorism cover is then bought back, in Great Britain, through the Pool Re scheme — see Pool Re and terrorism insurance. Because the two exclusions are adjacent, an event carried out by a state-linked actor with a political motive can engage arguments under both, and modern wordings increasingly define the boundary expressly rather than leaving it to the general law.

War exclusions in the cyber market

The pressure point in recent years has been cyber. Lloyd’s market bulletin Y5381, issued on 16 August 2022, required all standalone cyber-attack policies written at Lloyd’s (risk codes CY and CZ) to contain a state-backed cyber attack exclusion, applying at inception or renewal from 31 March 2023 unless Lloyd’s agrees otherwise. The bulletin set minimum requirements for those clauses. They must exclude losses arising from war, whether declared or not, where the policy has no separate war exclusion; exclude losses from state-backed cyber attacks that either significantly impair the ability of a state to function or significantly impair the security capabilities of a state; be clear as to whether cover excludes computer systems located outside any affected state; set out a robust basis on which the parties agree how a state-backed cyber attack will be attributed to one or more states; and define all key terms clearly. Managing agents were required to demonstrate that the clauses had been legally reviewed.

The attribution problem

The attribution requirement is the operative difficulty. Unlike a conventional war, a cyber operation does not announce its sponsor, and formal state attribution — where it comes at all — often arrives months or years later and is a political act. Model clauses published by the Lloyd’s Market Association address this in different ways, and the LMA groups compliant wordings into several types according to how broadly they exclude and how attribution is determined. The practical consequence for a buyer is that two policies can both satisfy the Lloyd’s requirement and differ substantially in what they actually leave covered, so the clause has to be read rather than assumed.

Non-affirmative cyber and CL380

A parallel strand concerns non-affirmative or “silent” cyber exposure in conventional classes. Marine and cargo policies have used the Institute Cyber Attack Exclusion Clause, CL380, since 2003 to strip out loss caused by the use of a computer or electronic system as a means of inflicting harm. Property and liability markets have followed with their own cyber exclusions and write-backs, and professional indemnity wordings deal with the boundary through the cyber exclusion in PI.

What a buyer should check

Read the war exclusion and the cyber exclusion together, because a loss can be argued under either. Ask whether the cyber policy’s state-backed exclusion is a broad “all state-backed attacks” form or a narrower “significant impairment” form. Check how attribution is determined and by whom. Check whether systems outside an affected state are within or outside the exclusion. And check that the war exclusions in the cyber tower and in the property and liability programme do not leave a gap between them.

Frequently asked questions

Is a war exclusion the same as a terrorism exclusion?

No. They are separate exclusions addressing different perils, although wordings often sit them side by side. In Great Britain terrorism cover is commonly bought back through the Pool Re scheme, while war is excluded and, if insured at all, is written in specialist markets.

What did Lloyd’s require for cyber policies?

Market bulletin Y5381, issued 16 August 2022, required standalone cyber-attack policies at Lloyd’s to contain state-backed cyber attack exclusions from 31 March 2023 at inception or renewal, meeting five minimum requirements covering war, significant impairment of a state, systems outside an affected state, attribution and clear definitions.

Does my cyber policy still cover a ransomware attack by a criminal group?

Ordinary criminal ransomware is not what the state-backed exclusion is aimed at, but the answer depends on how your clause defines a state-backed attack and how attribution is determined. Clauses that satisfy the Lloyd’s requirement differ materially in breadth, so the wording has to be read.

Related entries

• CL380 Institute Cyber Attack Exclusion Clause
• Terrorism insurance
• Pool Re
• Cyber exclusion in PI
• LMX spiral

This entry is part of the Apex Insurance Wiki. Last reviewed 2026-08-22. Next review: 2027-02-22. It is general insurance information, not legal advice, and it describes UK market practice and law as at August 2026.

Apex Insurance Brokers Limited is authorised and regulated by the Financial Conduct Authority (FRN 724952). This page is general information, not advice on a specific policy.