The North Atlantic Treaty Organization (NATO) has been around since 1949 and, in that time, there have been no major wars on the European continent.
There have been no major wars in Europe because attacking a member of NATO is the same as attacking every member of NATO. Invading a member of NATO would trigger a military response from every other member of NATO so an invasion is out of the question. Collective defense and solidarity doesn't leave any room for an aggressor pick off a vulnerable country like Poland before moving on to bigger targets like France.
You might say the entire point of NATO is to avoid fighting wars in the first place, but speaking to Fox News host Tucker Carlson, Trump floated the possibility that NATO could start a war.
“Membership in NATO obligates the members to defend any other member who has been attacked,” Carlson said to him. “Let’s say Montenegro — which joined last year — is attacked. Why should my son go to Montenegro to defend it from attack?” [...]
“I understand what you’re saying. I’ve asked the same question,” Trump said. “You know, Montenegro is a tiny country with very strong people… they might get aggressive, and congratulations, you’re in World War 3.”
Using Montenegro as an example here is interesting, but we'll get to that.
The only country that has ever invoked NATO's Article 5 right to collective defense is the United States. In fact, members of NATO are still in Afghanistan 17-fucking-years after we first invoked it. We're about to enter an era in which kids who weren't even born yet on September 11th, 2001 will be fighting the same war. How can we lecture anyone about collective defense?
Now, Montenegro's military is smaller than the average police force of an American city. They're not attacking anyone. They joined NATO so they don't have to attack anyone and so no one can attack them. At least not anymore.
In 2016 before Montenegro formally became a member of NATO, two Russian nationals and a handful of political oppositions leaders were arrested before they could launch a coup. An American witness just recently testified against the organizers of the coup last month.