Soldiers from 31 nations are mobilizing in the Arctic this week to participate in what North Atlantic Treaty Organization Secretary General Jens Stoltenberg reportedly said would be “NATO’s biggest exercise since the end of the Cold War.”

That quote from Radio Free Europe may have been either an exaggeration or taken out of context, but Norway’s Independent Barents Observer noted it will be the largest in Norway since the 1980s. According to US defense news website Military Times, it is also the biggest NATO exercise since 2015.

There were also conflicting media accounts as to the exact number of troops expected, with reports citing amounts ranging from 40,000 to more than 50,000.

Trident Juncture “will simulate NATO’s collective response to an armed attack against one ally,” Stoltenberg said earlier this month as quoted by Military Times.

“The scenario is fictitious but realistic,” he added. “And it will exercise our ability to reinforce our troops from Europe and across the Atlantic.”

“All members of the Organization for Security and Cooperation in Europe, including Russia, have been invited to send observers,” Stoltenberg said.

The exercise, which is set to include 150 aircraft, 65 sea vessels and 10,000 military vehicles, will begin on Thursday and run through November 23.

Trident Juncture comes a month after Russia held what it billed as its largest military exercise in nearly 40 years, with some 300,000 troops participating.