So in that sense you are absolutely correct.
But I invite you to think bigger. If one side lays siege to another side's city, and offers terms of surrender, the city needs to believe that the terms will be honored otherwise they don't surrender.
Which is a large part of European history during the period from the middle ages up until Napoleon figured out how to use artillery, i.e. hundreds of years of examples where "fighting honorably" was the winning strategy.
Notice that Germany and Japan are now strong allies.
Also notice that many people think the cause of WWII was that the WWI surrender forced unsustainable terms on Germany thus fueling the resentment that lead to WWII.
And many historians dispute it. Partly because those terms were standard for the time and better then what Germans themselves planned to enact after they win.
And partly because the German population never believed they lost the war. They believed they would winning absent "stab in the back". That is why the allies insisted on actually conquering Germany with no in between solution. The victory had to be absolute.
[0] https://en.wikipedia.org/wiki/Lost_Cause_of_the_Confederacy
if you can't count on your troops to be disciplined enough to follow your rules of engagement, how can you count on their discipline to follow your other orders? If you cannot show them that you are also disciplined, how do you expect them to maintain their respect for you as a leader?
If you don't have honor, what are you fighting for? Troop moral is what wins wars.
what's worse than death? Not having anything worth living for.
very very few people find honor in being the most evil person. And those few who do make very bad leaders; you either avoid having them in your armed forces or you limit their impact.
If one of your squadmates is an "I'll do anything to win" person, how can you trust them not to ditch you if that is their best survival option? Prisoner's dilema situations are common in battle
I encourage you to visit a US military cemetery. You will sometimes see shrines to the military virtues. Courage, honor, pride, family, discipline all rank pretty high.