Given similar basic personality types (independent initiative, etc), environmental conditions become the determining factor(s).
When I was a kid, I worked for a vet who had gone into Normandy on D-day 2. He was perfectly honest about being scared and how careful everyone was to hopefully not get killed.
A few years later, I worked with an older guy whose dad had been @ the Bulge. His dad told him that regular opposing troops were no more than 50 yards apart, and could clearly see each other. However, no one, from either side, bothered the other unless & until an officer showed up and made them attack.
The 'greatest generation' was just a cute marketing trick invented in order to sell books. The GG are like every generation - if times are flush, kick back and have a beer. If not, get down to business.
I once read that, even when in mortal danger, the majority of American troops would fire over the heads of the enemy. Despite their training, they couldn't bring themselves to kill.
I agree about environment being the normative factor. An adverse, even hostile, environment winnows out the self-servers and slackers. An environment marked by abundance encourages the lazy, the corrupt, and the mediocre.
Our (post-WWII) generation is a bunch of spoiled, self-indulgent whiners who consistently exaggerate our challenges and manufacture “crises” to enhance our tawdry legacy.
I doubt that many of this generation could rise to the challenge our fathers did. We might miss “American Idol.”