Not true at all. Does the Syrian Red Line ring a bell? A bluff was attempted then, it got called, and Obama welched, but it was still proof that threats can be made without a guarantee of commitment. If fact, that's pretty much how threats work. It's best if the individual making the threat is credible in terms of carrying out, but a whole lot of threats in geopolitics are just like threats made in life, bullshit.

I didn't say that threats cannot be made without a guarantee of commitment. They can be made, sometimes they work and sometimes they fail, and when they fail they make things worse. The Syrian chemical weapons red line was a good example of the latter.

That being said, would Putin have risked nuclear war by invading Ukraine if Biden hadn't made it crystal clear the US would not militarily intervene (we've intervened in every other way besides that, a full blown proxy war is still intervention).

Maybe

Would Xi? Is the power and ego trip for being the one who finally unified China be worth starting WW3?

Maybe

This is why POTUS are supposed to act a little unhinged and aggressive sometimes. So everyone in the world who is a bully at heart doesn't label them as a pussy who won't fight back and try to take advantage of them.

Also why Putin and Xi are supposed to act a little unhinged and aggressive sometimes. That's what bullies do. It's dangerous to make a non-credible threat to someone who is unhinged and aggressive.