LONDON — U.K. Prime Minister Keir Starmer and German Chancellor Friedrich Merz signed a landmark treaty on Thursday that pledges to tighten defense ties, as European nations try to protect Ukraine, and themselves, from an aggressive Russia in the face of wavering support from President Donald Trump's U.S.-focused administration.
“This is a historic day for German-British relations,” said Merz, making his first official visit to Britain since taking office in May. “We want to work together more closely, particularly after the United Kingdom’s withdrawal from the European Union. It is overdue for us to conclude such a treaty with each other.”
The treaty builds on a defense pact the U.K. and Germany, two of the biggest European supporters of Ukraine, signed last year committing to closer co-operation against the growing threat from Russia.
It includes a promise to “assist one another, including by military means, in case of an armed attack on the other,” though it's unclear what practical impact that will have, since both countries are NATO members and bound by the alliance's mutual defense pact.
Starmer said the treaty — signed at London’s V&A Museum, which is named after Queen Victoria and her German husband, Prince Albert — was a “statement of intent, a statement of our ambition to work ever more closely together.”
The U.K.-Germany treaty follows agreements signed during a state visit last week by President Emmanuel Macron, in which France and Britain pledged to coordinate their nuclear deterrents for the first time.
Germany does not have nuclear weapons. The treaty with Britain says the countries will “maintain a close dialogue on defense issues of mutual interest ... including on nuclear issues.”
The treaty stressed a “shared commitment to the security of the Euro-Atlantic area, and underpinned by enhanced European contributions” — a nod to Trump, who has demanded European NATO members greatly increase military spending. Germany and the U.K. have both promised to raise defense spending to 3.5% of GDP in the coming years.
People-smuggling gangs
Merz and Starmer also discussed topics including ways to boost European support for Ukraine, following Trump’s announcement of a plan to bolster Kyiv’s stockpile by selling American weapons to NATO allies who would in turn send arms to Kyiv.
The leaders announced that German defense startup Stark, which makes drones for Ukraine, will open a factory in England. They are also expected to agree to jointly produce defense exports such as Boxer armored vehicles and Typhoon jets, and to develop a deep precision strike missile in the next decade.
One key pledge was a commitment to boost investment and strengthen law-enforcement cooperation against criminal people-smuggling gangs using the English Channel.
Starmer has made it a priority of his center-left Labour Party to curb the smuggling gangs. About 37,000 people were detected crossing the English Channel from France in small boats in 2024, and more than 20,000 people made the crossing in the first six months of 2025. Dozens have died trying to make the crossing.
Berlin agreed last year to make facilitating the smuggling of migrants to the U.K. a criminal offence, a move that will give law enforcement more powers to investigate the supply and storage of small boats to be used for the crossings.
Merz is expected to commit to adopting the law change by the end of the year. Starmer said that commitment "is hugely welcome.”
Youth mobility agreement
Starmer has worked to improve relations with Britain’s neighbors, strained by the U.K.’s acrimonious departure from the European Union in 2020. He has sought to rebuild ties strained by years of ill-tempered wrangling over Brexit terms, and worked to reduce trade barriers and to strengthen defense cooperation.
But he has ruled out rejoining the 27-nation bloc’s single market or customs union, and has been cool to the idea of a youth mobility agreement with the EU.
The two countries agreed on a more limited arrangement that will make it easier for schoolchildren to go on exchange trips.
“I am glad we were able to reach an agreement so that schoolchildren and students can come to Britain more easily in the future, and the other way round can come to Germany more easily, so that the young generation in particular has an opportunity to get to know both countries better,” Merz said.
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Moulson reported from Berlin.
