He didn't participate as a ninja in the Third Shinobi World War; back then, he was still undergoing secret training with Danzo.
And Yamato wasn't someone interested in history; he hadn't studied the history of the Third Shinobi World War specifically, so he didn't know much about it.
"Naruto, your Ninja Academy's history class should have covered this, right? Why don't you talk about it?" Yamato said to Uzumaki Naruto.
"Huh? What Third Shinobi World War, did the school teach this? I have no idea." Uzumaki Naruto replied, utterly confused.
Obito found something familiar in Uzumaki Naruto's current demeanor; the sense of déjà vu was overwhelming.
"Naruto, if I may ask, how are your theory grades usually?" Kakashi glanced at Obito and then asked Naruto.
"Usually, I'm dead last," Uzumaki Naruto replied, a bit embarrassed.
Kakashi displayed an expression of 'as expected,' noting that Naruto's performance was not just similar to Obito, but exactly the same.
If it weren't for Naruto having the surname Uzumaki and a head of blond hair, Kakashi would've suspected some relation between him and Obito.
Obito felt momentarily blacked out; encountering a slacker with no prowess was just too vexing. At this moment, he fervently wished Uzumaki Naruto were a genius like Kakashi or Shisui, effortlessly acing everything.
Kakashi refocused on Yamato, realizing that relying on the underachiever Naruto was pointless. Though Yamato might not know much, any extra intel was still beneficial.
"During the Third Shinobi World War, Konoha engaged with the four major Ninja Villages one after another, and enemies infiltrated the Land of Fire several times." With no other choice, Yamato had to recall and recount what he knew about the Third Shinobi World War as best as he could.
He wasn't privy to many details, but he remembered some major events.
"Four major Ninja Villages!" Kakashi's eyebrows involuntarily furrowed. He had thought Konoha being declared war upon by the Three Great Ninja Villages was extreme, but then the Hidden Sand Village decided to enter the fray.
This made Mokgetsu's death in the Third Shinobi World War much more understandable. Facing so many powerful enemies, Konoha was surely lacking in manpower, and Mokgetsu, being strong, naturally had to bear more pressure.
This heightened the urgency in Kakashi's heart. As it stood, his strength was just too weak — merely able to defeat a normal Jonin wasn't enough to create any impact in the Ninja World War.
"Isn't it like all the great Ninja Villages ganged up to attack Konoha? That's just too despicable," Obito wished he could challenge those great Ninja Villages to single combat.
"Though Konoha faced the most challenges, the other Ninja Villages weren't united against Konoha. While warring with Konoha, the Hidden Cloud was also at war with the Hidden Sand, and the Hidden Rock with the Hidden Cloud, even the Third Raikage was killed in an ambush by the Hidden Rock Ninja Squad," Yamato explained.
If the four great Ninja Villages had truly united to attack the Land of Fire, Konoha wouldn't have stood a chance; during the Third Shinobi World War, Konoha didn't have a God of Ninjas-level force.
Hearing Yamato mention the Third Raikage's death in the Shinobi World War, Kakashi once again realized the dangers and brutality of war.
"Sorry, that's all I know," said Yamato with an apologetic look after speaking for about five minutes.
He felt that if Kakashi-senpai could travel back in time, he would surely help his past self change history, whereas he...
Kakashi put away his pen, rolled up the scroll, and solemnly thanked him, "There's no need for you to apologize; it should be us saying that."
Kakashi was well aware of just how audacious what he was doing was; he was actually daring to change history, to alter destiny.
If their actions resulted in failure, leading Konoha and the Ninja World to a worse outcome, then Yamato and Uzumaki Naruto, without having done anything wrong, would inexplicably become historical villains, so Kakashi felt a little guilty towards them.
"Kakashi-senpai, please do your best. I believe you can succeed," Yamato encouraged.
If it wasn't for the fact that the person requesting was the dependable Kakashi-senpai, Yamato's choice might have been different.
"Though Teacher Kakashi has many bad habits, he's never let us down. I believe in you, Little Teacher Kakashi; I'm sure you'll be fine. I'll have Brother Mokgetsu take you guys out for ramen afterwards," Uzumaki Naruto added.
Uzumaki Naruto was now quite eager to travel back; he hoped that once there, he'd meet the man who would share half his popsicle again, hoping to see Mokgetsu's warm smiling face, and wishing for the Mokgetsu Squad to remain as lively as ever.
"Don't make it sound like it's all up to Kakashi. He was once just my defeated opponent. Teacher Mokgetsu, Teacher Minato, as well as Rin and Asuma, I'll create a future with them in it!" Obito declared boldly.
He intended to protect all the people he cared most about, to safeguard all his friends, and he was willing to pay any price to achieve this goal.
"You're going to ride that one victory forever?" Kakashi responded, speechless.
He felt that losing to Obito that one time was one of the major setbacks of his life.
"Just say if I won or not," Obito stated, emphasizing that a win is still a win.
"Honestly, you two..." Nohara Rin remarked helplessly, "Hurry back and get some sleep; there's still a mission to continue tomorrow."
Obito and Kakashi, knowing better, exchanged a few more playful remarks before each returning to their rooms.