This started out as a simple factoid but grew into larger issues. I quite often learn by explaining.
Until recently biographers and commenters on JRR Tolkien have taken him at his word that he was not a good soldier during WWI. He believed he had done his duty but little more, and he specifically referenced his character of Sam Gamgee as the sort of person he thought a better soldier than he.
The great Churchill biographer Sir Martin Gilbert disagreed, and has taken some pains to contact Tolkien biographers and expositers and give them some background. He knew Tolkien in the 1960s at Oxfford and became friendly because Tolkien, as a Roman Catholic and Gilbert, a Jew, were not permitted to sit at the high table with the Anglicans and so got to know each other well despite a more than 40-year difference in age. He got only a little out of Tolkien about the Great War - unsurprising, given the times - but did later see that he had been told some things that had not made it into the general knowledge. Also, when he did his research for the Churchill books, he discovered a curious fact, that many WWI veterans described themselves as "not a good soldier" and even "a bad soldier." He decided that they could not all have been bad soldiers, and began to add this puzzle to his interviewing and his research.
He found that WWI soldiers, when asked who had been good soldiers, invariably identified those who had died. While the army, navy, and government would identify acts of heroism among the living and award them, the servicemen themselves did not mention this. Gilbert, knowing this by the time people were writing that his friend Tollers was being called a bad soldier, did a bit of research - he admits not exhaustive - and found that all indications were that he had been an excellent soldier. But the survivors didn't say that then. They never got together and decided this was going to be the party line, of course. But this was their culture, and they likely observed this in each other and wordlessly, even unconsciously, adopted this as the fitting response.
We have little conception what this was like. We have a volunteer army that is a small percentage of our population and do not comprehend the experience of other nations where many many were killed, many women widowed, and many children left fatherless. Individuals in our midst have some idea, yet even those do not have the experience of high school reunions that never happen because half the men are dead at 20, with graves untended and already being forgotten. Tolkien had a group of four close friends before the war. Only he and one other survived, so two of his three best friends before the war were killed, and 75% of his friends in the army. There are a few sections of LOTR that describe the death and destruction of war in WWI terms, such as the Dead Marshes and Frodo's emergence from them to the blasted destroyed lands outside of Mordor, and the repeated theme of honoring the dead. It is true that many cultures honor the dead and even the ancestors in general, so it is not unique to Northern mythologies nor to Tolkien, but it is quite prominent throughout, even in details such as the reference to the maker of the blade that killed the Nazgul
So passed the sword of the Barrow-downs, work of Westernesse. But glad would he have been to know its fate who wrought it slowly long ago in the North-kingdom when the Dûnedain were young, and chief among their foes was the dread realm of Angmar and its sorcerer king. No other blade, not though mightier hands had wielded it, would have dealt that foe a wound so bitter, cleaving the undead flesh, breaking the spell that knit his unseen sinews to his will.
Tolkien honored the dead throughout the work, and his characters who survive battles always make light of their own part.
We call it "survivor's guilt" now, and we used to try and reassure veterans out of it, reminding them that this was not their fault, they should not feel this way, etc. Yet I spoke with a friend who had moved to working with PTSD vets in the VA, who said that he and at least some others up here are not viewing it that way anymore. In the first place, saying "Don't feel that way" is pretty silly to begin with. But he also has begun to believe that anything that occurs this spontaneously and naturally across many people must come from our culture, our genetics, or some combination. It is not just an aberration, but something that works at some deep level for either the tribe or the individual. I asked my friend, who had grown up Roman Catholic but was now mostly nonpracticing (that changed when his daughter turned five, BTW, an example that I might humorously relate to Reviviscence without his permission), if this was related to the idea of us sacramentally sharing in the suffering of Christ with our own suffering. I clearly caught him off-guard with this, but he nodded that there was perhaps some deep psychological mechanism at work here. I would say that it was a deep spiritual mechanism that therefore influenced our psychology, but don't insist on it. He, at any rate, thought there was something long-standing in our make-up of honoring the dead by sharing in their suffering in this way, with the surviving soldiers being the bridge between the living and the dead. I am putting it much more neatly in retrospect than what he actually said. I wish I could discuss this with him, but he died a few years ago. For reference, if it gives any hint to you, he was a Vietnam combat vet from one of the heavily-purple areas of small-town Pennsylvania, who was alternatively an extreme libertarian and completely apolitical after living in NH for a few years and working as a psychologist. You can see why I would miss having him to talk to about issues like this.