I believe it was mostly because he could be turned into stone at any time. Wounds can be healed, and army's can be partially slain, but being turned into stone means you are basically defenseless against her until turned back, if you're turned back to normal at all.
The prologue of Romeo and Juliet serves to let he audience know the backstory of the play-set in Verona, two families are fighting, and that the deaths of Romeo and Juliet are the only thing that can stop the Montague/Capulet feud. Hope this helps you!
Answer:
read the back of the book gives great example of what you are asking
7: Complain
8: Breeze
9: Maintain
10: Spain
