Russian aggression isn’t limited to the annexation of Crimea or support for separatists in Eastern Ukraine. It extends to much of Europe, and provocations in European waters and airspace increase the risk of a military miscalculation that could spark an international incident — or worse.

There are many metrics, both official and unofficial, documenting the incidents. In just one of several examples, NATO’s Baltic Air Policing unit scrambled planes more than 150 times last year, which was four times more often than in 2013. Russian aircraft and naval vessels are probing well beyond the Baltics, however, and have tested the capacity — and patience — of several NATO nations.

Other recent incidents include a suspected submarine lurking near Helsinki, which led Finland’s navy to drop depth charges as a warning. And sometimes, according to a New York Times account, it’s not naval vessels but fishing trawlers caught up in the cat-and-mouse games. In recent weeks, two have snagged on suspected submarines, almost capsizing the boats in dangerous waters.

This kind of aggression has happened before, of course, but it should be a Cold War memory, not a present-day danger. And it comes amid unusually bellicose, irresponsible statements from Russian leaders about the possibility of using nuclear weapons.

NATO is responding with stepped-up defenses as well as recent training exercises in Latvia, Estonia and off Norwegian waters. That last location is where earlier this month 10 NATO allies — and Sweden, a non-NATO nation nonetheless concerned over the threat — began an anti-submarine warfare exercise.

“The NATO allies have to be prepared for any situation,” Kare R. Aas, Norway’s ambassador to the U.S. told an editorial writer during a May 4 visit to Minneapolis. “And that is why it is so important to strengthen NATO capabilities, and why it is so important to increase allied training. … Nobody should doubt the Article 5 commitments by NATO — they are for real. Which means that if one of the NATO countries [is] attacked, that is an attack on the allies.”

These commitments would be better backed up if NATO nations more consistently lived up to the alliance goal of spending 2 percent of GDP on defense, an objective few annually achieve. The U.S. will remain the backbone of the pact, of course, but the burden should not be disproportionate. It’s concerning that despite the threat from Russia, recent political and economic developments may be keeping some European leaders from maintaining their commitment to the alliance.

Along with military spending, diplomacy is needed to cool the rhetoric and convince Russian President Vladimir Putin that the military maneuvers are only strengthening NATO resolve and that a military mistake risks spiraling into a crisis that could result in a dangerous, destabilizing escalation.