Tailed Beast Control

Throughout the series, several shinobi, jinchūriki or not, have demonstrated the ability to gain control of one or more of the nine tailed beasts. The cause and effect of this control varies between those capable of doing it.

Jinchūriki
The jinchūriki have the potential to control their tailed beasts through sheer willpower and concentration, but requires a lot of training in order to retain them. If an inexperienced jinchūriki transforms deeper into his or her tailed beast's forms, his or her personality tends to corrode into animal instincts, becoming not only more ferocious in battle, but also increasingly dangerous to his or her friends and allies. The best training spot for a jinchūriki to control his or her tailed beast is at the Falls of Truth. For a jinchūriki to have complete control of the tailed beast within, one must have something to fill in the void within their hearts to give them strength.

According to Gerotora, it is implied that the tailed beasts' power consists of two parts: chakra and will. For example, whenever Naruto Uzumaki drew out a certain amount of Kurama's chakra, its will containing its hatred would fuse along with it, and if Naruto was completely succumbed to its influence, the seal would break and Kurama would be released. To control its power, Naruto must have his own will and heart both very strong and free of hatred, in order to separate Kurama's will from its chakra completely.

Gaara's control over Shukaku had increased in the beginning of Part II, where he could create and use its giant arms multiple times. Yugito Nii also had shown a high level of control, being able to fully transform into Matatabi with ease. In the anime, Utakata could assume the form of Saiken as well. However, their control was lacking compared to Yagura and Killer B's, as they became the jinchūriki to have complete control of their tailed beasts. Even though Naruto now has full access and control of Kurama's chakra, he was initially still unable to tame the beast itself. Due to recent events however, Naruto and Kurama have grown to trust each other enough so that Kurama is willing to share much of its chakra without trying to take Naruto over, and Naruto is willing to even open the seal behind which the beast is restrained. Seemingly finally taming the beast, he is now able to fully transform into the beast itself and make use of its considerable abilities.

Upon their resurrection, all the previous jinchūriki have displayed remarkable control over their tailed beasts, as Yugito, Yagura, Rōshi, Han, Utakata and Fū were all able to partially manifest them by displaying one of their tails (two in Fū's case, which enabled her to fly), and enter into "Version 2"-like forms, further showcasing their tailed beasts' strength, and even fully transforming into their respective tailed beasts.

When a jinchūriki is compatible with his or her tailed beast, the beast can act as his or her partner in battle. According to Killer B, once a jinchūriki has the tailed beast's cooperation and complete control of its chakra, he or she become immune to genjutsu, as the tailed beast can disturb its jinchūriki's chakra flow to break genjutsu. In addition, the tailed beast and its jinchūriki also have to have agreements of trading certain amounts of their own chakra, which can allow the jinchūriki to willingly transform into his or her tailed beast and be able to perform the Tailed Beast Ball without losing any control. Otherwise, the transformation without the tailed beast's cooperation will result in failure, and the tailed beast will then gradually consume its jinchūriki's own chakra whenever he or she uses the beast's chakra, which can kill the jinchūriki.

Non-Jinchūriki
Hashirama Senju, the First Hokage, could completely control the tailed beasts by using his Hokage-Style Sixty-Year-Old Technique — Kakuan Entering Society with Bliss-Bringing Hands, which utilises the power of his Wood Release kekkei genkai to forcibly suppress the tailed beasts' chakra. Yamato would later also acquire this power due to his genetic alteration, however by his own admission, to a lesser extent.

While both Madara Uchiha and Tobi could fully control the tailed beasts by using the standard version of the Sharingan, Sasuke Uchiha at first used his Sharingan to only suppress a small amount of Kurama's chakra within Naruto's subconscious. Tobi's method of control soon changed when he gained the Rinnegan, using the Outer Path's abilities to bind the tailed beasts with special chains of chakra. Danzō was also said to be able to probably be able to control Kurama with his Wood Element & Sharingan.

In the anime, Yūkimaru was able to partially control Isobu, the former tailed beast of Yagura.