In a war of attrition (actually any war or even battle for that matter) the war is generally won by the enemy's morale breaking, not by literally running out of soldiers. When one side is losing and they know they're losing (or they see the conflict as not worth dying for), most people would prefer to save their own lives rather than die for nothing.
So you get desertion, refusal to enlist, rapid surrender, and so on. This results in the losing state having to resort to ever more brutal means of conscription such as literally dragging people in off the street, making it illegal to film such actions, making it illegal to leave the country, expanding the age range for conscription, and so on.
That all results in even worse morale which makes your fundamental problems even worse. That, in turn, can motivate the losing nation to expend soldiers/resources on missions which may have some propaganda benefit, but ultimately serve no military purpose whatsoever. And at some point it all just collapses like a house of cards.
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And I think this fundamental issue of morale will be a perpetual in war. The winner will not be decided by who has the most drones, but by which side's morale breaks first. This is why Afghanistan, in terms of outcomes, is essentially the strongest military nation in the world. They've defeated both the US and the USSR in spite of being orders of magnitude behind in every single measure of military strength - except for morale. Those guys' spirit is simply unbreakable and they will fight you for decades, and to the last man, with absolutely no relenting.