This is precisely why Europe is becoming not just center or center right, but full on far right and ultranationalist. It is like these people do not realize the world they still live in. It is the ivory tower syndrome. People thought oh China would never dare try to challenge the US and Japan and yet you have them literally spend tens of billions of dollars to build unsinkable naval bases and landing strips on a small coral reef reclaiming land in the South China Sea in violation of every major international law.
People believed Russia would never dare until they openly invaded Ukraine, and annexed the Crimea and then helped Assad bomb the hell out of rebels. There is only one constant in the world, power, those who have it and wield it, those who want it and would do anything to get it. In a limited resource world, where freshwater may soon become the next gold or oil, where authoritarianism is just as prevalent on the global stage as democracy, it is foolish to think humans are not emotional or irrational enough to come to a world war again or that logic prevails over emotion.
If Britain won't come to the aid of a NATO ally when attacked, this is one of the largest and you could say most powerful military in Western Europe (sorry France), and if they won't intervene, NATO is truly a paper tiger and should be scrapped.