> similar line of argument about alliances and treaties preventing war was used before the First World War

NATO was formed with that in mind. A single treaty document publicly ratified. No secret pacts. No back-alley alliances.

It's also a bad concept. Defensive alliance is a loaded term, but people use it in arguments as if it was a well defined mathematical object.

> Defensive alliance is a loaded term

It also doesn't appear to be a very accurate description of the things NATO has been getting up to since the end of the Cold War.

"[NATO] has been involved in military operations in the Balkans, the Middle East, South Asia, and Africa"[0]

You don't have to be a spin doctor to realise that what seems like "defence" to one person is another's war of aggression.

German defence minister Peter Struck memorably said in 2004 that "Germany was also [being] defended on the Hindu Kush".[1]

[0] https://en.wikipedia.org/wiki/NATO [1] https://www.bundesregierung.de/breg-de/service/bulletin/rede...

> Defensive alliance is a loaded term, but people use it in arguments as if it was a well defined mathematical object.

Almost like "defensive weapons". Almost, because that's even worse.