War and the rules of war

Ever think about the rules in warfare? I have been recently, because for some reason they intrigue the hell out of me. It's almost surreal to imagine that guidelines exist for what essentially is a game of life and death.

I was in Fort Jackson in Columbia, SC a few months ago talking to one of the soldiers there. He serves as an infantryman, and he was explaining to me some of the rules that there are for ground troops in warfare. Some of them were interesting: things I would never have thought to do in a war but they are there to keep things humane, obviously. Seems paradoxical really. Anyway, here are some of the rules I can recall off the top of my head.

You can't shoot paratroopers out of the sky. You must first wait until they reach the ground to fire upon them.

You can't kill anyone with a ridiculously powerful gun (like, a chain gun meant for tanks. Something that would otherwise rip a person apart).

Unarmed medics are not targets. They are not to be fired upon.

Wounded soldiers are not targets, and are to be treated by medics as soon as possible, regardless of which country they hold their allegiance to.

I know that the rules have been followed in wars in history (WW1, WW2 for example) and thrown to the wind in others (Vietnam?) I'm not quite sure anyhow. Not the biggest history buff.

Anyhow, what do you guys think? I've always equated war with the idea that it's every man for himself as far as you and your enemy go. Defeat them at all costs, right? The implimentation of rules make it seem a lot more like a game with a huge cost. It's weird that I've lived this long and really have overlooked the idea that our leaders send us to essentially play a big (albeit much more costly) chess game in order to gain power over something. If I ever go to war, on one hand I can see myself seeking vengeance upon the person that killed the friend and comrade that went in with me, but on the other hand I can also see myself rationalizing that the person that fired the gun isn't responsible for the death of my comrade, but just another piece in his leader's game. It's the leader thats responsible, right?

Agree/disagree? Additional comments?

Also, sorry for my poor writing. I'm sleep deprived at the moment, so hopefully it reads okay to you guys.

Jam it back in, in the dark.