Baelinor

Lol, not confusing. Genin historically is a common term for 'lower person' or 'low rank person'; similar to peasant, serf, slave or similar type structure. Recruitment for many organizations came from the genin and the shinobi was no different. They were still referred to as genin even after recruitment, though their job/clan may have changed. In any case this is a superhero game and historical stuff gets bent to fit the fantasy anyway and the shinobi myth has a lot of stuff already built in. You had just asked for historical references is all and shinobi would be more appropriate in that time period. Interestingly the word ninja has made it into English dictionaries and the plural, ninjas is purely English (Japanese doesn't have plural in the English sense, so in Japanese you would not say ninjas) while shinobi is still just Japanese.

True, I should have referenced the word 'language' in my comments, I was trying to avoid some of the nuances you are putting forward. However, like you said, Ninja wasn't in general use until after WW2 so doesn't really fit the theme going on here. Shinobi would be more appropriate given the time period, but to each their own.

A terminology note, for what you are using, the term 'elite forces' might be better than special forces. Special forces (SF) or even special operational forces (SOF) has a different meaning than what you are using, US Marines are not SF (though within the marines there are SOF). The German military unit called Stormtroopers are WW1 units, the Stormtroopers (SA) of WW2 are a paramilitary unit (they were not military) also called brown shirts that provided security for the Nazi party (amongst other things). Germany had a Marines equivalent called the Marinestosstruppkompanie (or MSK). US and German commandos of WW2 have already been mentioned. Also, Ninja is Chinese, Shinobi is Japanese (Shinobi no mono, proper). Of course this is me just being a stick in the mud... For weapons, most infantry had access to similar weapons. But to add to the list, Marines also used shotguns (an oddity but very good in trench warfare and aboard ships), M1A1s (bazooka), mortars as well as other things mentioned (they had snipers, light/heavy machine guns and the flamethrowers). Here is a handy website where you can see a list by country https://ww2db.com/weapon.php For the Japanese officers, you might go along with the Bushido code which was wide spread. In WW2 this translated into doing anything for the emperor (which 'excused' them to do some of the less pleasant things they did like unit 731 and self sacrifice). Pain domination has some abilities that fit in like shared pain, world of pain, anguishing cry or enforce moral. However, you could go down the standard samurai ki shout (howl or psychic scream). These seem more appropriate (to me) than caltrops. Afraid I don't know much about the Italian officers. There was one officer, Tito Agosti, who got the Knights Cross for fighting "to the limit of human possibilities" before being wounded and captured you might take inspiration from. So maybe call the trait Enduring and give them Triage Beacon or Soothing Aura? Or maybe Determined and give them something from the leadership pool.