That theory also guided the development of the EU, which has arguably been a significant source of peace and stability for the past 70 years, leading to great prosperity. This is only the second war we are seeing on the European continent in all that time. Compared with the previous 70 years it's quite an achievement.

It's a fallacy to focus on the one failure of the policy and ignore the other cases when it was working.

As for NATO its expansion all the way to the borders of Russia didn't prevent the war either, and it remains to be seen whether we won't end up with a war between Russia and NATO.

In times of war it's tempting but dangerous to feel like militarisation of the world is the solution. History doesn't show that to be the case in general.