The treaty was signed at the Battle of Britain Bunker at RAF Northolt in west London, a location chosen for its historical resonance given the significant role played by Polish pilots in the Battle of Britain. The two prime ministers described Russia as the most significant long-term threat to European security and expressed the need to counter its malign actions.

The treaty text identifies “the Russian Federation as the most significant long term threat to that security and the need to counter its malign actions,” and commits both parties to “countering and deterring Russian aggression and interference in all its forms.” Both governments also resolved “to apply appropriate pressure on the enablers of Russian malign activity and aggression” and to work together to hold Russia “including its political and military leadership, to account for its violations of international law.”

Starmer said the treaty marked “the biggest step forward in our defence and security relationship with Poland in a generation,” adding that “Britain and Poland are already close allies and friends, but the challenges Europe now faces demand an even stronger partnership. Our collective work together will keep our countries safe for years to come.”

Tusk said the treaty had raised Polish-British relations “to the highest possible level” and would help “secure Poland and other countries against the Russian threat.” He added: “We want to defend Polish and British security; we want to protect cyberspace; we want to strengthen NATO as a whole — this is the essence of our treaty.” He also said: “History teaches us, and geography teaches us in a particularly painful way, that Poland must build credible alliances that will, above all, deter potential aggressors.”

On defence cooperation, the treaty commits both parties to “enhancing bilateral interchangeability and interoperability between their respective armed forces across all domains, including via enhanced joint training, education, and exercising” and to “supporting the defence industries of the Parties and their common projects, including developing joint capabilities, and enhancing co-operation in research and technology, inclusive of technology transfer.” The two nations also commit to joint procurement, greater alignment of defence industrial and export strategies, and work to identify and minimise regulatory barriers to joint programmes.

The treaty text states that in the event of an armed attack on either party, they “shall assist one another, including by military means in accordance with Article 5 of the North Atlantic Treaty.” Both parties reaffirmed what the text describes as their “ironclad commitment to NATO as the bedrock of their security, and the foundation of collective defence of the Euro-Atlantic area.”

The agreement also covers hybrid threats, with both parties committing to “share strategic approaches to the growing threat from hybrid activities, including, but not limited to sabotage, and the malign use of technologies such as artificial intelligence and drones.” Cooperation on countering foreign information manipulation and interference, cyber threats, counter-terrorism intelligence sharing and critical national infrastructure protection all feature in the text.

The treaty builds on a 2017 defence and security cooperation treaty and a 2023 joint declaration. According to reporting in Polish media, Tusk compared the accord to a treaty Poland signed with France in Nancy last year and said bilateral agreements of this kind, alongside NATO, the US alliance and the EU’s SAFE defence financing programme, form the basis of Poland’s broader security strategy.