South and North Korea certainly do have the capacity and recent historical precedent of waging a war against each other. The last attack of North Korea on South Korea was on November 23, 2010 [1]: "North Korean forces fired around 170 artillery shells and rockets at Yeonpyeong Island, hitting both military and civilian targets." That's less than 8 years ago. This is why North Korea acquiring nukes is scary: it's not completely unreasonable to imagine that the Korean War could resume.

I don't think in recent history France has engaged its army without either a mandate from the UN (Libya, Ivory Coast, etc.) [2], or being called for help by a local government according to a bilateral defense treaty (Mali). Maybe you have a counter example? Of course you can always go further in the past: France didn't become one of the largest European country by not waging expansionist wars... But I'm not sure it's entirely relevant to the world we are currently living in.

[1] https://en.wikipedia.org/wiki/Bombardment_of_Yeonpyeong

[2] Of course it doesn't mean that the result is always good: Libya is a giant cluster fuck now.