Not well developed would be to our advantage if the casus foederis were in a grey area.

(It's somewhat :lolsob: to note that Thucydides already distinguished between "stated reasons" and "real reasons" behind a conflict; remember "Remember the Maine!"

https://en.wikipedia.org/wiki/Casus_belli#:~:text=Proschema,... )

EDIT: looks like there may not even be a need to be part of an existing mutual defence alliance; sending troops to take part in Operation Arctic Endurance might suffice for an Art 51 response to invasion?

https://opil.ouplaw.com/display/10.1093/law:epil/97801992316...

3(a) and 3(d) refer to: https://iilj.org/wp-content/uploads/2016/08/General-Assembly...