Be it about an individual or a group, heroism can only apply to a specific behaviour going beyond what is normally expected from her/him/them, which includes taking great risks (usually his/her/their own lives), and is valued by the community. So, simply being a military cannot equal being a hero.

Furthermore, we must look at what is valued. The young Nazi (or the young communist) who denounced his parents as enemies was looked at as a hero by his community, whereas we see him as a monster. On the other hand, should we see a German soldier risking his life to save his friends a hero?

So heroism as nothing to do with the military. It applies as well to the civilians whose behaviour fits these criteria, such as these villagers who saved thousands of Jews during WWII and to anybody who takes great risks to do the right thing.

My father was drafted as an officer in 1939, fought the battle of France and was a prisoner in Germany from 1940 to 1943. I don't think anybody saw him (and he never saw himself) as a hero for that. However, after being liberated by the Germans (under the scheme named La Relève), he joined the French Résistance in the Alps. My uncle entered the Résistance and became secretary of the National Council of the Résistance, was arrested, tortured, and deported to Dachau. For me, they could be seen as heroes, even if I (and they) never used this word.

BTW, here is a a quote from one of the economists founding fathers (from Lyon!):

« Partout les armées ont attiré d'autant plus la guerre et les maux qui l'accompagnent, qu'elles ont été plus redoutables : il n'en est aucune qui ait préservé son pays d'une invasion. Le vieux proverbe, si vis pacem, para bellum, était bon chez les anciens, où la force décidait tout ; il n'est plus chez les modernes l'expression de la vérité : de grands préparatifs de guerre mènent toujours à la guerre. » Jean-Baptiste Say

" Everywhere armies have attracted even more war and the ills that accompany it, as they were more formidable: none has preserved his country from an invasion. The old proverb, "si vis pacem, para bellum", was good among the ancients, where the force decided for everything, while it is no longer among the moderns the expression of the truth: great preparations for war always lead to war. " Jean-Baptiste Say

"Dieu se rit des hommes qui se plaignent des conséquences alors qu'ils en chérissent les causes" Jacques-Bénigne Bossuet