This is not an easy question to answer and no one can really predict the future. I imagine if an all-out war were to break out between Israel and Arab countries in the Middle East, a lot would depend on what kind of weapons were used.
Either way, millions of people would be killed. If one or more countries were to use nuclear weapons, our whole planet could be in danger. If one or more countries were to use chemical or biological weapons, again, our whole planet could be poisoned. Rather than asking what would happen, pray for peace and look to see what you can do to prevent it. Don’t use social media to stir up bad feelings, use it to promote peace.