Poland and France will guarantee each other's security under a new treaty signed in Nancy on May 9, Prime Minister Donald Tusk said.

The agreement, which includes mutual military assistance, marks the first time France has extended such a commitment to a non-neighbouring country.

The Treaty on Strengthened Cooperation and Friendship also covers collaboration in the defence industry, economy, agriculture, science and space. Tusk said that a similar agreement with the United Kingdom would follow soon.

Under the treaty, the Polish and French armed forces will enhance interoperability through joint exercises, deployments in strategic regions and multinational operations.

It also provides for officer exchanges and joint military education. In the event of an attack, both countries pledge mutual support, including military action, in line with the United Nations Charter, the Treaty on European Union and NATO’s Article 5.

"From today, France and Poland will truly be able to count on each other in every situation. We are giving each other mutual security guarantees and you can be sure that President Macron and I intend to take this commitment deadly seriously,” Tusk said at a press conference.

Tusk also said the treaty would bring "concrete operational actions" in defence industry collaboration, strategic planning and crisis preparedness.

The treaty commits both sides to joint threat analysis, joint military drills and facilitating the transit and stationing of each other’s troops on Polish and French territory.

French President Emmanuel Macron said the agreement "opens a new page of history", highlighting France’s readiness to mobilise forces when necessary. Not having a treaty with Poland, "a great European partner", had been "an anomaly" now corrected, an unnamed Elysée official told Politico.

"The organisation of our armed forces, the investments we continue to make and the quality of these forces mean that we are able to engage these resources in case of possible aggression," Macron also said.

Since Russia’s invasion of Ukraine in early 2022, Poland has become NATO’s top defence spender relative to GDP, which is projected to reach 4.7% in 2025. A major buyer of American and South Korean weapons, Warsaw is, however, under pressure to involve more European partners while preserving strong ties with Washington.

Potential deals involving France include Poland purchasing Airbus A330 MRTT tanker aircraft and expanding cooperation in submarines, artillery ammunition production and the European Long Range Strike Approach missile programme, which includes Poland, France, Germany, Italy, Sweden and the United Kingdom.

Beyond defence, the treaty promotes collaboration in cybersecurity, quantum technology, artificial intelligence and space exploration, with plans for future joint industrial projects.

France and Poland will also inaugurate a Polish-French Friendship Day on April 20, marking the anniversary of the entombment of double Nobel Prize winner Marie Skłodowska-Curie and her husband Pierre Curie in Paris.

To commemorate the occasion, Tusk presented Macron with a rare collection of Skłodowska-Curie’s correspondence with Albert Einstein.