NATO will launch its biggest military exercises in decades next week with around 90,000 personnel set to take part in months of drills aimed at showing the alliance can defend all of its territory up to its border with Russia, AP reports citing top officers.

The exercises – dubbed Steadfast Defender 24 – “will show that NATO can conduct and sustain complex multi-domain operations over several months, across thousands of kilometers (miles), from the High North to Central and Eastern Europe, and in any condition,” the 31-nation organization said.

Troops will be moving to and through Europe until the end of May in what NATO describes as “a simulated emerging conflict scenario with a near-peer adversary.” “The alliance will demonstrate its ability to reinforce the Euro-Atlantic area via transatlantic movement of forces from North America,” NATO’s Supreme Allied Commander, U.S. General Christopher Cavoli, told reporters.

Cavoli said it will demonstrate “our unity, our strength, and our determination to protect each other.”

The chair of the NATO Military Committee, Admiral Rob Bauer, said that it’s “a record number of troops that we can bring to bear and have an exercise within that size, across the alliance, across the ocean from the U.S. to Europe.”

Bauer described it as “a big change” compared to troop numbers exercising just a year ago. Sweden, which is expected to join NATO this year, will also take part.

U.K. Defense Secretary Grant Shapps has said that the government in London would send 20,000 troops backed by advanced fighter jets, surveillance planes, warships and submarines, with many being deployed in eastern Europe from February to June.