> will assist the Party or Parties so attacked by taking forthwith, individually and in concert with the other Parties, such action as it deems necessary
https://www.nato.int/cps/ie/natohq/topics_110496.htm
If Poland triggers Article 5, just because fallout came to its borders, other members are free to send them iodine tablets and lead tents, rather than starting WW3.
It's not a start nuclear Armageddon article.