>>/52476/
> mutual defense agreements
This could be a broad term, and could include stuff liek:
> thereby we vow that if Ukraine is attacked by Russia again, we'll sanction Russia (again) and send our concern to Ukraine (again)
But in a strict sense which would cause these most important NATO countries to go to war against Russia: no. They won't risk it.
The chief problem is however - as far as we can tell - that noone knows how Ukraine will look like after the war, or even in half a year distance that could be after the war btw, I linked an article here >>/52417/ that notes Ukraine could lose during this winter.