White Zetsu Army

These artificial creatures are Madara Uchiha's and (later) Obito Uchiha's creations that are essentially clones of Hashirama Senju, that was developed using his DNA. They most notably include his right hand-man, Zetsu as well as a large number of other Zetsus which serve as Akatsuki's main military strength during the Fourth Shinobi World War.

Background
First specimens of these creatures were artificial humans created by Madara Uchiha from Hashirama's living clone, and the Demonic Statue of the Outer Path. Because of this, their DNA is very similar to that of Hashirama Senju's as noted from Shizune, and Sakura Haruno's autopsy results. Madara would later use this artificial genetic material to save the life of Obito Uchiha, replacing the destroyed portion of his right side with it.

During Obito's time with the elderly Madara, White Zetsu and a spiral-patterned Zetsu were assigned to take care of him during his rehabilitation. Later, when Rin and Kakashi were attacked by a group of Kirigakure-shinobi, the spiral-patterned Zetsu allowed Obito to "wear" his body like armour so that he could leave the cave. White Zetsu, who was only half formed, would be infused with a part of Madara's will that results in his transformation into the completed Zetsu who would serve under Obito as both joined the Akatsuki years later.

Eventually, Obito created more (about 100 000) humanoid versions of White Zetsu using the chakra of the first seven tailed beasts he had sealed within the Demonic Statue of the Outer Path. The resulting clones were then stored in a pool of water beneath the root of the living clone flower. After Kabuto Yakushi captured Yamato, he used his studies of Hashirama's DNA and Yamato to enhance the army's strength.

Personality
Aside from original Zetsu and Spiral Zetsu, clones created by Obito have shown some level of intelligence, similar to other clones. Although they were seemingly fighting mindlessly against allied shinobi during the daytime, the clone who had transformed into Neji Hyūga using his Substitute Technique, was noticeably scared by Sakura Haruno when she threatened to beat him and showed shock when she deduced how his technique worked as well as the tactics of the Zetsu army's night assault. They were also visibly shocked and angered when they realised that Sasuke Uchiha had killed White Zetsu, whom they refer to as their original. In the anime, a clone encountered by Team Kurenai displayed the carefree and somewhat goofy attitude of its original. The anime also depicted the clones as having the memories of the original and the way Madara and one of the clones talked to each other confirmed that.

Appearance
Unlike the original White Zetsu, and the clones he produces, which possess incomplete bodies, they have complete faces, as well as properly defined right arms and legs. After Kabuto used Yamato (who also possessed Hashirama Senju's DNA) to further enhance their abilities, the Zetsu clones gain small spiky protrusions on their shoulders and back. These Zetsu, however, lack the Venus fly trap-like extensions that the original had, and have what seems to be cracks all over their bodies. They also have a zig-zag pattern running down their midsection, and also down each leg reminiscent of the originals' fly trap-like extensions. These serrations are later shown to be able to open in a similar manner and restrain targets. In the anime the clones are completely white like the original, wheras in the manga, they appear light-green. In later depictions they appear even more green in colour.

Abilities
Being artificial humans, they do not need to carry out any normal human bodily functions. They also have no need for sleep nor other bodily functions such as breathing in the case of their underwater storage. Though they share many vital points as a normal human, they are incapable of bleeding in their natural forms. As such they are extremely durable, able to survive two of Sakura's chakra-enhanced punches, as well as Neji Hyūga's Gentle Fist Art One Blow Body.

All Zetsu able to use the Mayfly technique to travel through surfaces for the purpose of spying without leaving a trace. They can open their bodies in a Venus flytrap-like manner to trap their opponents and absorb their chakra. In the manga, the clones absorb chakra by simply establishing physical contact, whereas in the anime, the clones absorb chakra by sucking it in through their mouths. This action is so the clone responsible uses the Substitute Technique to become an exact copy of that person in every detail, able to easily trick close friends and sensors alike, in scenarios ideal for infiltration, covert assassination, and causing distrust among an enemy group. Due to their plant nature, members of the White Zetsu Army can merge into a more plant-like monster for better resistance against Yang-natured chakra. In the anime, it was shown that the White Zetsu clones can also extend the points of their flytrap-like openings and use them to impale enemies, as well as alter the form of their arms to attack.

Due to the fact that they were created through cultivation of Hashirama Senju's cells, Sakura states that the White Zetsu Army can also use Wood Release, albeit on a weaker scale. However, through exposure to Yamato's chakra, the clones' strength increased to make them presumably more suited for combat with enhanced strength. But the one genetic flaw to the White Zetsu's design is that direct contact with a powerful concentration of Yang-natured chakra causes them to turn into trees.

In the anime, the White Zetsu Army showed their capability to take on the properties of a special, poisonous, red soil, located on the Seventh Front and use it to their advantage; such as expelling large quantities of red, poisonous smoke. However, the adverse effects of this was that they also gained the soil's high conductibility to lightning-type attacks.

Confining the Jinchūriki Arc
After creating an alliance with Kabuto, Tobi leads him underground and shows Kabuto his army of 100,000 White Zetsu clones in an underwater cavern beneath the Demonic Statue of the Outer Path.

Shinobi World War Arc
Once Tobi finished his preparations for the Fourth Shinobi World War, he had the Zetsu army mobilise to fight the Allied Shinobi Forces' 80,000-person strong army. Because of the size of their forces, Tobi has the Zetsu travel below ground, to be led from above by himself to hide their numbers. This was discovered by Muta Aburame and is reported to the various commanders. The Second Division, led by Kitsuchi, as well as elements from the Fifth Division, unearth and attack a detachment of 20,000 White Zetsu Army clones travelling directly underneath them. While fighting the Allied Shinobi forces, they began to overwhelm them, allowing several thousand White Zetsu to pass through underground.

Then, off the coast of the Land of Lightning, several thousand White Zetsu Army clones appeared along with Kakuzu, Hizashi Hyūga, Asuma Sarutobi, Dan, Kinkaku and Ginkaku to attack Darui's First Division, forcing the Allied Shinobi Forces to change their strategy to meet this threat. By the end of first day of battles, the army had already lost 50,000 out of its 100,000 Zetsu, leaving Tobi's army at half strength.

During the night, the White Zetsu used the Substitute Technique to sneak behind enemy lines disguised as allied shinobi in order to kill various members of the Allied Shinobi Forces and cause conflict among the opposition. However, assuming the identity of Neji Hyūga to go after medical ninja, one of the clones was found out and stopped by Sakura Haruno. Soon after, along with Sakura and her group learning their enemy's true nature as hybrid clones of Hashirama, the White Zetsu clones' technique was deduced and reported to HQ.

In the anime, Team 8 was sent to investigate a suspected breach of the Allied Shinobi Forces perimeter and encounters a cave filled with White Zetsu clones. Engaging them, Hinata sends out a messenger owl to the Sealing Team and she alongside, Shino, Kiba, and Akamaru, hold off the opposition until the team can arrive and seal the cave. As Team 8 fall back with the creatures in pursuit, one of the White Zetsu accidentally triggered a explosion in the process. After the explosion, Team 8 regroups and find one of the two shinobi from the Sealing Team dead, the ninja revealed to have been murdered by a surviving White Zetsu that had infiltrated Team 8 in midst the chaos. This cases mutual mistrust among Team 8 until they use a game of rock-paper-scissors to weed out the shape-shifter by having the loser reveal personal information when asked. Though Kiba mistook Shino as the impostor, the plan exposes the White Zetsu clone, who was impersonating Hinata who was unconscious at the time, before her team mates kill him.

While Naruto and Killer B confronted several of the White Zetsu Army clones at another area, due to his Yang chakra and the creatures' relation to the First Hokage, Naruto's attacks while in Nine-Tails Chakra Mode resonated with the White Zetsu Army clones and instantly turned those he made a direct hit on into trees. Even after some of the surviving White Zetsus merged to become more resilient to the youth's attack, Naruto merely cut the fused monster in two and crushed it beneath Gamahiro. Naruto eventually sent his clones out to the different battlefields and, using his ability to sense negative emotions, was able to locate the remainder of the disguised White Zetsu Army clones and neutralise them.

Later, in the anime, Omoi goes to the Seventh Front, where two thousand White Zetsu killed the Amphibious Search and Destroy Unit, and were after the Thundercloud Unit; a supply squad formed by notable children from Kumogakure. The Seventh Front was surrounded by a special red soil, which the White Zetsu were able to take on the properties of, causing them to gain a red tone and expel a red, poisonous smokescreen from their mouths and bodies. After saving the children, Omoi, with Thundercloud Unit's assistance, was able to dispel the smokescreen from the area with the Lightning Release Co-Operation: Thunder Bomb as well as defeat the remaining White Zetsu.

After the second day of war, thanks to the addition of Naruto's efforts and his new-found ability, the majority of the White Zetsu clones were eradicated. However, small factions survived and were ordered to seize B and Naruto before their comrades could reach their location. When Sasuke escaped the Mountains' Graveyard, he encountered one of these factions, who demanded to know why he left the hideout. Upon coming to the realisation that he had killed the original White Zetsu, they attacked him. Choosing this time to test his new powers further, he slaughters most of the Zetsu and keeps one alive long enough to acquire information relating to the war.

Return of Madara Arc
As Madara faced off against the tailed beasts, one of the clones managed to recover the right Rinnegan from where Obito had hidden it. He gives the eye to Madara who also severed the clone's right arm to replace his own. After Madara succeeds in subduing the tailed beasts and prepares to remove the Eight and Nine-Tails from their respective jinchūriki, the Zetsu suggests that Madara instead start with the One-Tail for better efficiency, to which Madara agrees on. The clone subsequently questioned why Gaara had been fighting to help Shukaku, despite the fact that he was no longer his jinchūriki.