To both of you, without an armistice, the countries involved do not have a reason to stop fighting. More often than not, the armistice allows for compromise and a "be all end all". I guarantee you without the armistice there would still be fighting between the countries. To put this in a Naruto perspective, Nagato's attacks on the shinobi countries would just prolong the "Cycle of Hatred", true to the mannerisms of war in real life. You need a declaration of peace to (temporarily) halt fighting and attempt to promote peace between countries.
if all we needed was an armistice then why did we drop the bombs? Nagato would force the shinobi world to peace through total war with super weapons, its the same exact ****ing thing.