As it was mentioned before, war is just another things that "follow the times".
Speaking about chivalry, I too agree that it's important, but it's better to stay alive because honour can be regained, whereas life can't.
The way wars are executed nowadays are focused, as you'll agree, on specific things. 1) Keep minimum loses on your side 2) Don't hurt civilians (in an ideal world, sure..) 3) Win by doing the minimum possible yet most efficient damage on the enemy. In a simplistic way, the ideal weapon would be a long range beam that'd hit the enemy's HQs and destroy everything electronic, rendering them unable to retaliate.
Ok, in a more serious manner now, there have been indeed improvements that we may never properly understand.
The first that comes to mind is the fact that nowadays, you get to suffer less (at least if injured in a battle). An injury by any type of blade or arrow/bolt that would not kill you instantly, would've let you suffer for far longer than an injury by a bullet. Moreover the latter has less chances of letting you live as a cripple (not that it doesn't happen). Why do you think bayonets were banned when the humanitarian culture pressured the governments to agree on rules that should be followed by the waring nations? If things now seem too easy or too cowardice if you want, things back then were brutal, really brutal. Clashing armies counted thousands of men and very few remained unscratched. While weapons are increasing in potential, the number of soldiers that need to be involved is decreasing.
Secondly, the so-called "smart weapons" are still under development and we'll start seeing their use only in the future (God forbid but you understand what I mean). Let's say the atomic bomb was never used. Then, in order to reach the same conclusion to the war, we'd have loses from both sides in a number of battles. That weapon cut it in half, nullifying losses from one side. That however was done in an unforgivably crude way and I surely lament the moment it was used. And that's why they're trying to further improve it. Next time they'll have more control over the atomic procedures, the casualties will be lessen and the environmental damage as well. And, like I said, if anyone can find a way to carry out a war without anyone dying won't that be a great improvement? A most cowardice way to do things but a very welcomed one.
In the end, what is chivalry? You can't expect to see things like in rpgs, where you take turns hitting each other. Or, let's say, stop using snipers (who I believe are a very efficient way to conduct war, not a battle, but war in a bigger scale) because the opposing side won't have a chance to fight back. There's a reason why agreeing in an armed duel will get you in prison in most, if not all, countries.
The single greatest and most importance value in today's world is the human life, not the human ego. Everything's moving towards the direction that promotes this principle.