Britain and Germany signed a wide-ranging friendship treaty on Thursday, deepening ties in areas ranging from defense to transport, marking Friedrich Merz's first trip to London as chancellor, the latest visit to help reset UK ties with the EU.

Merz's day trip follows a three-day state visit to Britain by French President Emmanuel Macron, signaling greater cooperation between Europe's top three powers at a time of threats to the continent and uncertainty about their U.S. ally.

Europe has been confronted with new U.S. tariffs since President Donald Trump returned to the White House, as well as questions about the U.S. commitment to defend its European allies.

"The treaty is, on the one hand, a sign of the normalization of German-British relations after Brexit," said Nicolai von Ondarza at Berlin's SWP think-tank. "On the other hand, the treaty is a sign that the UK has become even more important as a security partner due to transatlantic uncertainty."

Germany has similar friendship treaties with just a handful of countries, like France, underlining the closeness of their ties.

Coming nearly a decade after Britain voted to leave the European Union, the treaty includes a clause on mutual assistance, which is "highly significant" in light of the ongoing Russia-Ukraine conflict, said Ondarza.

It builds on a defense deal agreed last year that included the joint development of long-range strike weapons, and comes after France and Britain agreed last week to reinforce cooperation over their respective nuclear arsenals.

Deeper defense

As part of Thursday's announcement, Britain and Germany pledged to "pursue joint export campaigns" to drum up orders from other countries for equipment they make jointly, such as the Typhoon Eurofighter jet and the Boxer armored vehicle.

That could help boost sales and represents a significant reversal from the previous 10 years, when Germany blocked Saudi Arabia and Türkiye from buying Typhoons.

Typhoons are made by a consortium of European companies, including BAE Systems in Britain and Airbus in Germany, with the different partner governments responsible for orders to different countries. Meanwhile, German-British joint venture Rheinmetall BAE Systems Land produces the Boxer armored vehicle.

Further deepening ties, German defense technology company Stark has agreed to build a new factory in Britain, its first production facility outside of Germany, to create AI-powered unmanned systems.

Beyond defense, the treaty also includes an agreement to develop a new direct rail link between the two countries and jointly combat irregular migration, as part of Starmer's push to reduce the number of asylum seekers arriving in Britain to counter the populist Reform UK party.

Germany pledged to outlaw the facilitation of illegal migration to Britain, with a law change by the end of the year.

That would give law enforcement the tools to investigate warehouses and storage facilities used by migrant smugglers to conceal dangerous small boats intended for illegal crossings to Britain.