I see this that lets go to war means let us ulter the existence of certain economic progression. Apart from death of people both soldiers and the civilian, it take back the system backward from the party in the war but the effect is more on the people not in the fighting, the world at large
War is something I don't think any individual or nation would want to be in. That's why every possible means to avoid it if possible is been sort for but, the need to exercise some form of sovereignty or be in charge of your own territory and avoid influence often makes it in editable in conflict situations and resolutions.
In war, people get to lose there homes and means of livelihood, infrastructures and civilization that took years yo build or developed is reduced to dust in minutes or hours. It's such a hard thing to take. The good thing about it is that, through all these, humanity have been seen to find a way to better ourselves.
After the field is laid plane, an opportunity for new ideas is born and it teaches men to avoid situations that could lead to war at every reasonable cost. I say reasonable because, when your sovereignty is been challenged, it's hard not to result to war.
I think your first part is very meaningful because you said that a nation doesn't want to be in war. That implies an important differentiation because often it is not the people who want the war, but the government for ideological reasons. I don't know how many Russian civilians really want the war in the Ukraine, but if I had to guess I think it is not that many. Losing your children while you don't even know or never understand what it was good for, that can't be in the interest of the civil population. So the "nation" usually doesn't want war, while the leading apparatus of that nation might force it go to war.
The destruction we are seeing in war areas is so intense these days. It often looks like there never even has been a single building. Heaps of rubble everywhere, dead people lying left right and center. No energy, no water, no heating and children get born without medical care. Not even food.
I disagree in one regard with you: you said that humanity has been seen to find a way to better ourselves. Do you really think so? There come two ideas to my mind.
The first idea is that the weapons are so deadly today, especially the nuclear arsenal, that we do indeed have a global geopolitical strategy mainly based on military deterrence. Aggressors know that if they go too far, their county would eradicated from the world map, but then probably the whole world would be destroyed anyway. It only needs a few evil minds and we could indeed have a nuclear war. Do we have such an evil mind on the planet right now? I can't say yes, but I also can't say no.
The second idea is that war has only seemingly become less brutal because a hundred years ago there was less artillery and more close contact combats. That was brutal. Watching your enemy in the eyes while killing them is the worst one can imagine. Today you have way less close contact combat. That makes it easier for people to push the button. But think about it: does that make us any better than the people from a 100 years ago? When we conduct military operations as if we were playing chess or a computer game? That's the brutal part of today's war as empathy is close to zero once you marked your target on the screen and push fire. It is only digital. It is about coordinates, about software, about a canon that can fire miles and miles and miles. Dead people are no faces anymore, but numbers.
I get what you are saying @Smartvirus and I have been thinking about that question myself a lot. But the whole drone game slowly but surely feels like war has turned into a board game for its most part and we all know that board games feel much better on the inside than actually truly killing another body with your own hands.