German submarine-hunting planes will operate out of Britain under a "milestone" agreement between Europe's biggest defence spenders, the governments announced Tuesday.
Boeing P-8 aircraft will patrol the North Atlantic from a base in northern Scotland, as the NATO allies respond to the threat from Russia after its 2022 invasion of Ukraine.
The Trinity House Agreement, to be signed in London on Wednesday, will also see German arms giant Rheinmetall open a UK factory making artillery gun barrels, using British steel.
In a joint statement, UK Defence Secretary John Healey and his German counterpart Boris Pistorius said the pact would "strengthen national security and economic growth in the face of growing Russian aggression and increasing threats".
The agreement is the first between the UK and Germany.
The artillery factory would support more than 400 jobs, while the two countries will undertake joint work to develop deep strike weapons that can travel further with more precision than current systems, including Storm Shadow cruise missiles.
The two armies will train together more often in a bid to strengthen NATO's eastern flank and German P-8 aircraft will periodically operate out of Lossiemouth in Scotland to "help protect the North Atlantic".
"The Trinity House Agreement is a milestone moment in our relationship with Germany and a major strengthening of Europe's security," Healey said.
"We will build on this new cooperation in the months and years ahead," he added.
Pistorius said the deal was evidence that "the UK and Germany are moving closer together," following 14 years of Conservative rule that saw the UK exit the European Union.
"We must not take security in Europe for granted," he warned.
"Russia is waging war against Ukraine, it is increasing its weapons production immensely and has repeatedly launched hybrid attacks on our partners in Eastern Europe.
"With the Trinity House Agreement, we are showing that the NATO Allies have recognised what these times require," he added.