It was a massacre, directed by the Fourth Hokage, Minato Namikaze. The stars were Kakashi Hatake and Obito Uchiha, with Rin Nohara and Nawaki Senju in supporting roles, along with a host of extras being slaughtered: the Demon Race.
The gap in strength between the two sides was simply too vast to bridge. Even throwing sheer numbers at them to wear them down would not work. That was the adjutant's most immediate impression. Only now did he understand why the general had been so wary of spatial power.
Nawaki Senju's Wood Release: Deep Forest Emergence surrounded them. Any demons who tried to flee were entangled by the trees, which drained their power. There was simply no counter to it. Meanwhile, Kakashi and Obito seemed to share an unspoken understanding, calmly dodging, coordinating, and cutting down enemies amid the onslaught of tens of thousands of demons. In particular, to coordinate with Kakashi through his Rinnegan, Obito had given him a black rod beforehand. Kakashi understood immediately and drove it into his left shoulder, after which the Nine-Tails' chakra fused the rod with the wound.
Seeing what Kakashi had done, Obito laughed. "Aren't you afraid I'll use that to control you?"
Kakashi chuckled. "Heh, I trust you. Besides, even if you wanted to control me, you couldn't. All right, here they come." Kakashi prepared for battle, and Obito smiled as he got ready to coordinate with him. Through the black rod, Obito also shared his Rinnegan's vision and the power of the Heavenly Dao with Kakashi.
It was their first time using the Rinnegan's shared abilities, and the sensation was extraordinary. Kakashi and Obito seemed to have two fields of vision at once, yet it did not feel strange at all. It was as though they had been born with the ability.