Oddly, the US Army actually teaches sleeping during Basic Combat Training. In order that they won't seem "soft," though, it's done indirectly, in that one first spends six weeks sleeping less than 6 hours a night (6 hours if you're lucky, but with 3-4 nights of 1-hour duty shifts interrupting during the week), and three days (over 70 hours, yes) with no actual sleep to speak of.
Yes, after 48+ hours, one does start hallucinating. There's just nothing quite like shooting tracer rounds at plastic Communists in the dark when the wraiths are playing bridge in the foxhole beside you and you're pretty sure you saw a white rabbit with a stopwatch.
On the other hand, it's probably a lot cheaper than most street drugs.
But what's this someone said about brain damage? That would explain so much of the code I've been left by those "code faeries" who come after I thought I were asleep...