From Robert Heinlein's "Starship Trooper":
There are a dozen different ways of delivering destruction in impersonal wholesale, via ships and missiles of one sort or another, catastrophes so widespread, so un-selective, that the war is over because that nation or planet has ceased to exist.
What we do is entirely different. We make war as personal as a punch in the nose. We can be selective, applying precisely the required amount of pressure at the specified point at a designated time - we've never been told to go down and kill or capture all left-handed redheads in a particular area, but if the tell us to, we can. We will.
We are the boys who go to a particular area, at H-hour, occupy a designated terrain, stand on it, dig the enemy out of the holes, force them then and there to surrender or die. We're the bloody infantry, the doughboys, the duckfoot, the foot soldier who goes where the enemy is and takes him on in person. We've being doing it, with changes in weapons but very little change in our trade, at least since the time five thousand years ago when the foot sloggers of Sargon the Great forces the Sumerians to cry "Uncle".
Maybe they'll be able to do without us someday. Maybe some mad genius with myopia, a bulging forehead, and a cybernetic mind will devise a weapon that can go down a hole, pick out the opposition, and force it to surrender or die - without killing that gang of your own people they've got imprisoned down there. I wouldn't know; I'm not a genius, I'm a ... Infantryman.
In the meantime, until they build a machine to replace us, my mates can handle that job - and I might be some help on it, too.
Maybe someday they'll get everything nice and tidy and we'll have that thing we sing about, when "we ain't a-gonna study war no more." Maybe. Maybe the same day the leopard will take off his spots and get a job as a Jersey cow, too.
But again, I wouldn't know; I'm not a professor of ... politics; I'm an ... Infantryman. When the government sends me, I go. In between, I catch a lot of sack time.