You touch many interesting themes here.
WWI, the shift to the war of XX century - at least until Vietnam, that changed the paradigm again - offers many path for historico-philosophical reflection (or speculation).
First of all, what made those men so prone to kill in those days?
For the vast majority I guess the answer could be
decency. Men had to go to war as citizens, not as men. It was their duty. (Nations that have some "You shall" embedded are clearly more ready to become magnificent soldiers...). This would open a whole new thread of discussion about the modern state, at least in the form we have known in Europe since the French Revolution - and it'd be off-topic.
Other element to consider is that death was a lot more present in the daily life back then. I have no exact knowledge of the statistics, but I guess that only a new-born out of two could expect to become forty-years old. "
A clean death, a soldier's death" was a way to cheat fate, somehow.
And, yes, bravery was a factor too. But what is being brave?
We have focused mainly on violence here, but violence it's not an aim - at least it used not to be.
I think that the last
intellectuel that actually carried a reflection of this sort was probably John Milius.
A movie like
The wind and the lion shows well what was driving them when engaging in a fight. The film represents a sort of clash of civilizations, 3 actually: Europe, the Arabs (ethnically Moroccans are not exactly Arabs, but the civilization footprint fits the description, compare with
Lawrence of Arabia), and the rampaging US, waving Teddy's
big stick.
Notwithstanding their differences, they share common values in the fight, based on chivalry and honor, where violence was only a side effect. (The duel scene between El Raisuli and the German officers is very telling in this sense). In a way the film asserts that their common chivalry code is what unites them in mankind.
IMO their honor code represents a common need, felt by youngmen of then and now, for a trial, for an initiation, for taking part into some event or process that truly achieves the biological growth of the boy into a man. It's a symbolic sacrifice where men put their life at stake in the attempt to become true men ( I am just trying to guess their perception -
axioms?, I am not saying that warriors are the only true men). By they same process these men would also achieve recognition by their peers, become active memebers of their community and get somehow, like Iliad's heroes, one form of eternal life accessible to mankind.
Without disrespecting current opinions on war, I find this initiations a more authentic growth of man, not purely intellectual and/or economical as nowadays. Because it does not take only the mind to make an adult, the trial implies a radical know-yourself experience which is ultimately unspeakable.
Milius is also the author of the screenplay of
Apocalypse Now. This is,
inter alia, a deep reflection that from violence shifts to the nature of man, which comes to annihilates himself looking deep down in the abyss of
horror - or down the abyss
tout-court, horror emerges as the radical essence of man and being.
Is violence the exertion of the connection between a subject and his true being?
Ever thought that violence is the more radical form of knowledge? As some Oriental doctrines affirm, annihilation is the ultimate knowledge/experience for the sage?
These are my thoughts, whenever I watch the last awesome (no other word is possible) scene of
Apocalypse Now, when Kurz is killed - indeed a sacrifice offered to the abyss, where Kurtz is the willing victim.
This
philosophical trip was clearly not in the mind of the average soldier of WWI, or preceding wars. Still, I can't help drawing a line between this and the metaphysics in the
Birth of Tragedy.
Maybe this thoughts - which are not really such, rather a sort of general feeeling about everything, a radical reset of all belief and expectations, maybe even a wholly new nihilistic
Weltanschauung - could explain how come Rimbaud stopped writing poems and eventually started trading weapons (and maybe this thoughts would explain why Rimbaud wrote his poems in the first place).
But this
cupio dissolvi is probably specific to Europe, I don't know how much it's been exported elsewhere in the world - although Jim Morrison, somehow, knew all this.