The British-led war games are code named Joint Warrior and the numbers are all big: 13,000 personnel from 14 countries operating more than 50 ships and submarines as well as 70 aircraft.
NATO says the planning started long before Russia began behaving as an adversary.
For more than a year NATO
has been condemning Russia's actions in Ukraine as well as its frequent, large scale, snap military drills and those long-range Bear bombers repeatedly flying very close
to NATO airspace.
So, if Joint Warrior is not a deliberate response, it's certainly a timely one.
CNN was invited to spend a day aboard one of the vessels taking part -- the U.S. Navy's guided missile cruiser USS Vicksburg. It's the current flag ship of a standing NATO maritime group.
Commanding officer Rear Adm. Brad Williamson says Russia's behavior is an added motivation to do well in these exercises.
"Anytime you have a security situation that reminds us it's not just a game we're doing out here, that there are real world implications to our ability to provide security to alliance members, I think that focuses our minds on what we're doing," Williamson says.
Other personnel on the Vicksburg tell us competition between different nations and even individual ships and subs is also a big motivator.
The details of these war games are top secret. But they're broken into two parts: The set training exercises that involve vessels or groups completing specific jobs and what they call "free play".
That's where everyone's divided into two teams with different orders and motivations manipulated by the game masters. Tensions rise and it's likely pretend war follows. Easy to see how things get competitive.
Russia has taken an interest. It used its right under what's known as the Vienna document to send its own inspectors. NATO says they only stayed a few days and didn't see anything sensitive.