I think I have a theory with regards to Kaguya and why she would want soldiers. It might be kinda insane, that’s where this manga is right now, yes?
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So, it’s stated by Black Zetsu that Kaguya wants soldiers. But for what? Apparently everyone in the world is trapped in the genjutsu, so who is there to fight?! After having read the chapter on a website I usually read from, I was looking through the comments, some of which were people jokingly (or maybe not?) saying that Kaguya was going to wage interplanetary war. This is obviously coming from when Naruto had spoken with the SOSP, when Naruto had asked if he was some kind of alien, with the Sage replying that he wasn’t too far from the truth.
This made me recall about “The Tale of the Bamboo Cutter,” which is obviously where Kaguya is coming from, with Kishi’s love of incorporating Japanese myths and folklores in this story. If you don’t know the story read here for a summary:
https://en.wikipedia.org/wiki/The_Tale_of_the_Bamboo_Cutter#Narrative
So, Kaguya in “The Tale of the Bamboo Cutter” was a celestial maiden from the Moon. If this is has been incorporated into “Naruto,” this might explain that alien comment. Another thing to possibly note is that when Naruto questioned where Kaguya had come from, the Sage refused to answer. It’s only hinted she’s from a faraway place.
Going back to "The Tale of the Bamboo Cutter", quoting the Wikipedia page, it’s said “in some versions of this tale, it is said that she was sent to the Earth as a temporary punishment for some crime, while others say it was for safety during a celestial war…” For “Naruto,” let’s focus on the former.
Now, we return to the question: what exactly does Kaguya need soldiers for? If Kishi incorporates the fact that Kaguya did indeed come from the Moon (and was perhaps sent down as a punishment), does she want to wage war on the Moon people?
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TO SUMMARIZE, Kaguya is from the Moon, she was banished maybe, and she wants to wage war with Moon people using humans turned into White Zetsus to fight.
I honestly have no idea. I could be so dead wrong about this. Again, the theory is kind of insane, but it’s just what came to my mind.