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An attack on one ally is an attack on all. That is Article 5 of our founding treaty, and that is ironclad.

Jens Stoltenberg

Remarks on collective defense during a visit to the U.S. Capitol, 2023 · Checked on 3 March 2026
An attack on one ally is an attack on all. That is Article 5 of our founding treaty, and that is ironclad.

Analysis

The statement directly references **Article 5 of the North Atlantic Treaty (1949)**, which states that an armed attack against one member shall be considered an attack against all, requiring a unified response. Stoltenberg’s characterization of it as 'ironclad' aligns with NATO’s longstanding public messaging and its invocation only once (after 9/11). No evidence suggests the commitment is conditional or weakened. The phrasing matches official NATO documents and speeches by prior Secretaries-General.

Background

Article 5 is the cornerstone of NATO’s deterrence strategy, designed to prevent aggression by guaranteeing a collective response. It has been reaffirmed repeatedly, including at the **2022 Madrid Summit** and in responses to Russia’s invasion of Ukraine. Stoltenberg’s remark reflects NATO’s emphasis on unity amid rising geopolitical tensions.

Verdict summary

Jens Stoltenberg accurately quoted NATO’s **Article 5**, which establishes the principle of collective defense as a binding, 'ironclad' commitment among allies.

Sources consulted

— North Atlantic Treaty (1949), Article 5: [https://www.nato.int/cps/en/natohq/official_texts_17120.htm](https://www.nato.int/cps/en/natohq/official_texts_17120.htm)
— NATO’s official FAQ on Article 5: [https://www.nato.int/cps/en/natohq/topics_110496.htm](https://www.nato.int/cps/en/natohq/topics_110496.htm)
— Remarks by Jens Stoltenberg at the U.S. Capitol (2023-06-21), NATO transcript: [https://www.nato.int/cps/en/natohq/opinions_216236.htm](https://www.nato.int/cps/en/natohq/opinions_216236.htm)
— 2022 NATO Madrid Summit Declaration (reaffirming Article 5): [https://www.nato.int/cps/en/natohq/official_texts_196969.pdf](https://www.nato.int/cps/en/natohq/official_texts_196969.pdf)