Arguably modern war is a highly negative selection force.
In ancient times the best warriors were more likely to survive, and they had their pick of the losers women, as it was acceptable to breed from them. See the Iliad for a thorough introduction to this mindset.
The probability of death or incapacitating injury in modern war is nearly random, while the most dangerous military jobs are selected for among the most fit. So we expose our best to a random probability of death. And the survivors don’t get extra women.
I touched on that, at the macro level. Within the war zone itself, it is providing selection in various ways. Whether good eyesight and reflexes (for instance) is more beneficial than an abundance of caution is a good question.
"In ancient times the best warriors were more likely to survive,"
That I'm not at all sure about in general. Certainly sepsis and other issues took many that would survive today. Just as in today's world, the matchup of forces made a huge difference. Americans in the Middle East are far less likely to die if hit than their counterparts on the other side, for instance.
"and they had their pick of the losers women, as it was acceptable to breed from them. See the Iliad for a thorough introduction to this mindset."
The Iliad would be worth a reread at this point, good idea.
"The probability of death or incapacitating injury in modern war is nearly random, while the most dangerous military jobs are selected for among the most fit."
Most "fit" in terms of physical condition - not necessarily so overall. The "fitness" metrics cover the entire gamut, not just the physical.
"So we expose our best to a random probability of death. And the survivors don’t get extra women."
I'd argue that the survivors have better access to a large segment of the female population. I'd be willing to bet that most of those who've been in combat are ready to raise a family, often a large one (demographics aside).
But, it certainly isn't the same as in ancient times. How many descendants does Ghengis Khan have again? lol
(For those who don't know, somewhere over 100 million.)