Why we fight (there was an old B&W movie by that name IIRC)

Alan (very thoughtfully, I thought) said:
What keeps soldiers at the sharp end from making themselves scarce when
the whizzbangs start to fly? Firstly, there's the fear of letting down
your mates. But also, there's tradition: our ancestors (even if they
weren't blood relations) managed to do (insert heroic deed here) so we
have the capability to do the same. So we *can* overcome our fear. And
not merely that, but tear those enemy bastards limb from limb and rip
their throats out with our teeth if neccessary.

[Tomb] You develop, I believe, a very low opinion of the value of the
other guys life when you realize he's willing to kill you. You become
much more ready to kill him first at that point. This is part of the
demonization/objectification training that most military institutions
use, but it is also human nature. If you've gotta have fight or flight
hormones raging, from a win or die situation perspective, you want the
fight hormones going for your unit members. 

So it doesn't matter that those who fought at Anzac Cove are long gone,
nor that not a drop of their blood flows in our veins. They did it: we
can too.

To everyone upon this earth
Death cometh soon or late
But how can we die better
Than facing fearless odds
For the ashes of our fathers
And the temples of our gods?

[Tomb] The choice is yours soldier, 
When the grey day draws nigh, 
Bright day to live, 
Grey day to die. 

Finally, there's another very important thing: the reputation of units.
Australian infantry has the (deserved) reputation of being indomitable
shock troops. Their reputation scares the bejayzus out of the
opposition. And that's a huge advantage. Success breeds success, and
failure breeds failure. That's why Regimental traditions are so
important - and conversely, if you're up against an opponent with such
traditions, you're going to have to fight twice, thrice or more times as
hard, as they won't quit.

[Tomb] Espirit de Corps comes from the belief that your comrades will
bust their asses not to let you down, so you have to bust yours for
them. You've been through hell together and your instructors have broken
you down as an individual and built you up as a team. You learn you lose
as one individual but win as a team and there is nothing you can't do as
part of that team. And part of that is inculcation in the great deeds
(we tend to ignore the mediocre periods and actively forget the bad
days) your antecedents did. Yes, you don't have any blood connection,
but you both wore the same uniform. In some way, coming up short would
be failing them. Most of the time, you'd rather die (or risk dying) than
do so. Strong tradition coupled with indoctrination breeds a strong will
to win (and also a strong confidence that you can). Success does indeed
beget success, and some legends are built on. I'm quite sure Gurkhas
aren't quite as fierce as the legends indicate (while still waaaay
fierce), but they're canny little guys who understand the advantage of
their fearsome rep (and they have black humor) so they play it up. This
makes them _more_ effective, not less. If the enemy is willing to
crumble at the mention of your name, then it makes life safer. OTOH, it
means that sometimes you have to live up to your rep and pay the piper.
But by then, you've got the weight of tradition, precendent, ancestors
(in a military sense), and institutional memory all riding in your
rucksack.