Madara enters the fray and the Ten-Tails is unleashed.
However, because the Naruto anime franchise spans two series, there is often confusion regarding where this arc takes place. The vast majority of the war takes place in Naruto Shippuden , but the final battles and the conclusion of the war bleed into the sequel series, Boruto: Naruto Next Generations (via flashbacks). what episode is the 4th great ninja war