Polish Prime Minister Donald Tusk and British Prime Minister Keir Starmer signed a new defense and security treaty in London, United Kingdom, on May 27, according to statements from both governments the same day. Named the Northolt Treaty, the agreement covers jointly developing a new air-defense missile, conducting large-scale military exercises and coordinating efforts to counter Russian hybrid attacks.

The agreement builds on earlier deals the two countries signed in 2017 and 2023 covering areas like military training and cybersecurity, with talks on the new, larger treaty running since January 2025. It also fits a wider network of bilateral defense agreements that both have pursued with partners in Europe and beyond in recent years. The United Kingdom recently struck strategic partnerships with Norway, France and Germany, while Poland has signed agreements with France, Sweden, South Korea, Japan and Canada, and is close to concluding an enhanced defense pact with Germany.