Reinforcements Arrive

is episode 321 of the Naruto: Shippūden anime.

Summary
In the battlefields no one is able to tell White Zetsu Clones from their comrades and are all in a state of confusion. Naruto's shadow clones later appear at every division to their rescue. Later on at Headquarters, they find out that "Madara" has arrived with revived jinchūriki. However, it later turns out that Mū is still alive and has summoned the real Madara Uchiha to the battlefield.