Is a person’s way of life and economic prosperity also worth defending? If so, nuclear weapons are not sufficient. All another country needs to do is cut that person’s country off from the rest of the world. Bring it down from the inside. No invasion or war required.

> The neat thing about nuclear weapons is that if you only care about self defense, you don’t need anything else.

Nuclear weapons have no proportionality, so it's bad to rely on them for defense. If you do rely on them, you're either going to start WWIII over a border skirmish, or your enemy is going to chip away at you because you won't.