Military buildup

I suspect we're seeing just the opposite effect to that proposed by the OP.

Too be sure, armaments have increased in cost almost exponentially but firepower can be delivered with a theoretical accuracy that was only dreamed of in the Cold War era. Armed drones are far less destabilizing than fleets of bombers.

Most of the 30,000+ nuclear weapons deployed in 1989 have been dismantled, their fissile material often recycled as fuel for civilian power plants. The 40,000 Soviet tanks that were once perceived to be ready to pour across the Inter-German border have mostly become consumer goods after being scrapped as unnecessary. Chemical weapons arsenals have been mostly destroyed, there are fewer aircraft carriers at sea than at any time since the London Treaty was signed in 1930 and ideological differences between the global powers are not really seen as a cause for armed conflict anymore.

It seems that people have forgotten that the overwhelming tendency is for developed countries to wage war against each other in times of plenty, when surpluses can be spent freely and massive internal debts incurred to pay for it all. Right now nobody can afford to war on a whim and negotiation for disputed resources in invariably cheaper than combat when cash is low.

My wife considers me an incurable pessimist, something that I would certainly agree with but I really think that global war or even war between regional superpowers is off the table for the foreseeable future. To be sure, there will be speed bumps, assorted crisis' and the odd angry shot, but a repeat of the numbered World Wars or even a significant regional conflict in the early 21st Century is very unlikely in my opinion.

Opinion offered up with the caveat that you can't fix stupid so fear, demagoguery, paranoia and greed can change this prediction in unpredictable ways.