I would like to add to @ViktorijaT's fantastic answer by adding that if we all develop the 'cosmic perspective' as defined by the atrophysicist Neil Degrasse Tyson.
This is the link to an audio with a beautiful instrumental: give it a watch only 5 mins but there is nothing more beautiful than these words which if we all apply them and think about them, we'd cease drawing divisions.
This is a vital question so thanks for raising this discussion! What is happening in the world right now is devastating and heartbreaking. I can't imagine how people on both sides feel and are dealing with the situation. I really hope it's going to end soon..
In my opinion we can stop this war by giving Ukraine more support (I heard they need more air defense). I mean I know this might not be very smart for most countries to go all in on Ukraine's side (since Putin might nuke them), but following the situation from a far and not doing enough is kinda worse. Again, I'm not saying I'm an expert this is just my opinion.
I'm also interested in preventing this from happening ever again. It's clear to see that history is repeating itself and we know that "insanity is doing the same things and expecting different results".
In my opinion a more holistic approach might solve some if not the majority of our issues. I know we might be far from the ideal, but if we try to mold the next generations by those principles we will for sure see a shift in the upcoming 50 years for sure.