I realize that an end to war is about as inconceivable as us ending our reliance on oil.
But, for just a minute - walk with me here.
If it came to pass that I had to pick only one thing to pass along to the generations that will follow mine, it would be this:
Embrace your inner-agnostic. It's not like it's going to kill you to try, so learn that it is okay for us all to find our hope in different deities. Stop killing each other because you are fighting a war rooted in religion. And, just in case you didn’t know it yet: They are almost ALL rooted in religion and almost always have been.
Treat others the way you would want to be treated yourself, not because you believe in a higher power, who either will or will not hold you accountable, but because you know instinctively that it is the right thing to do.
Accept that there are going to be as many different ways to play nicely as there are people on this planet, and if we all just started being reasonable we could start the process of stopping this silliness.
Surely we’ve evolved enough by now to realize that there have to be better ways to share this space and quit sending our sons and daughters out to fight wars where nobody walks away a winner. We have to be nearing the time when we start to realize that these wars are extracting enormous costs and just yielding more wars. Seriously. We've walked on the moon, we can talk on telephones that aren't attached to a wall and we have toasters. How hard can it be?
There is little (like, zero...zip) evidence to support the notion that we are out-growing this need to eliminate each other in the name of "God" or "Allah" or "The Flying Spaghetti Monster" (or whomever) and we are frighteningly over-due for some critical thinkers to stare directly into the eyes of this one and suggest change, plot a course and motivate the masses to lean into it.
Play nice, no biting, no knife-play and quit trying to kill each other in the name of a deity who may or may not exist. Learn to share your stuff, your land, your water, your freedom and your ideals. Do not expect everyone to agree with you and see that for the thing of beauty that it is.
Embrace the differences, kids... play nice.
Please note that this is IN NO WAY directed towards the people who are actually doing the bidding, suffering and dying for the people in power who call the shots. In my world, soldiers will occupy a place in heaven that will be much more comfy than the rest.