1.What do you mean natural disasters? How can a military stop an earthquake? XD
2.We have the police to fight crime, not an army. Sending an army against a bank robber is over doing it, don't you think?
3.If another country declares war on them, they can always try to make deals and treaties to get things figured out.
If USA never attacked Iraq, there would be no ISIS...If WWI never happened, nether would have WWII.
You can NEVER get total peace from war. The only thing war bring is more war...