White Zetsu Army

The White Zetsu Army was a large attack force that was created by Madara and Obito Uchiha utilising White Zetsu. The first attempt to create an army from White Zetsu happened long ago, when Kaguya Ōtsutsuki gained the ability to mould chakra from the God Tree. The army comprised Akatsuki's military strength in the Fourth Shinobi World War.

Background
The White Zetsu were originally humans that fell victim to Kaguya Ōtsutsuki's Infinite Tsukuyomi and were assimilated into the God Tree. Over the course of years, the victims morphed into their current forms, having their original personalities and individuality drained away. Kaguya created the army in order to combat two invaders who planned on coming to Earth to steal her chakra for themselves. The two ultimately never arrived in her lifetime and Kaguya, having degraded into the Demonic Statue of the Outer Path, was sealed within the moon by her two sons, while the White Zetsu came to reside inside the Demonic Statue under unknown circumstances.

Centuries later, Madara Uchiha awakened the Rinnegan and summoned the Demonic Statue out of the moon. In order to survive beyond his natural lifespan, Madara used the statue to cultivate Hashirama Senju's DNA into a non-sentient clone contained within a gigantic flowering tree in a cave beneath Mountains' Graveyard, and subsequently connected himself to said tree to continuously receive the statue's chakra. Madara believed the White Zetsu that appeared on the tree were clones of Hashirama created as an unintended result of his experiments, and that Yin–Yang Release was somehow involved in their creation. In actuality, Black Zetsu had simply released the White Zetsu stored within the statue without Madara's knowledge.

Madara later used Hashirama's artificial body to save the life of Obito Uchiha by rebuilding the destroyed right portion of his body, granting him a body similar to that of a White Zetsu. Presenting themselves as artificial humans created from the Demonic Statue's power, White Zetsu and Tobi oversaw the young Uchiha's rehabilitation while Madara slept. Later, when Rin Nohara and Kakashi Hatake were attacked by a group of Kirigakure shinobi, Tobi allowed Obito to "wear" his body like a suit so that he could leave the cave. White Zetsu, whose body wasn't fully formed, would later be infused with Black Zetsu, who Madara believed to be a manifestation of his will. The complete Zetsu went on to become a member of Akatsuki, while continuing to serve directly under Obito.

Using the Demonic Statue's chakra, the White Zetsu propagated. By the time of the Fourth Shinobi World War, 100,000 White Zetsu had fully developed and were stored in a large pool of water beneath the roots of the flowering tree. According to Obito, these White Zetsu were created using a large amount of the chakra of the seven tailed beasts Akatsuki had sealed inside the statue. After Kabuto Yakushi captured Yamato, he used his studies of Hashirama's DNA to enhance the White Zetsu's strength, suspending Yamato inside the flowering tree beneath Hashirama's clone.

Personality
The White Zetsu demonstrate some degree of individuality and intelligence, with one claiming that they have vocabularies and brains that surpass those of humans. Although the White Zetsu that fought in the Fourth Shinobi World War initially seemed to fight mindlessly against the Allied Shinobi Forces, they have been shown to possess a similar level of intelligence. One, which transformed into Neji Hyūga demonstrated both shock and some degree of fear when Sakura Haruno threatened it and deduced how its abilities work, while others were visibly shocked and angered when they realised that Sasuke Uchiha had killed White Zetsu, whom they refer to as their "original". Those White Zetsu have been shown to have access to the original White Zetsu's memories, and also appear to share his personality.

Appearance
Unlike the original White Zetsu and the parasite clones he produces, which possess incomplete bodies, the White Zetsu that fought in the war have fully developed faces and bodies. After Kabuto used Yamato to further enhance their abilities, the White Zetsu gained small, spiky protrusions on their shoulders and back. Though they lack the Venus flytrap-like extensions of the original White Zetsu, they have zig-zag patterns running down their midsections and legs, which are able to open in a similar manner and restrain targets. In the anime, the White Zetsu are entirely white, save for their green hair and yellow eyes, whereas in the manga, their bodies appear light-green. Later, they appeared even more green in colour. Eventually, they're depicted fully white as in the anime.

A variation of the White Zetsu is seen to be massive in size and built with scythes for hands and three Zetsu heads.

Abilities
No longer 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 are 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, they absorb chakra by simply establishing physical contact, whereas in the anime, they absorb chakra by sucking it in through their mouths. This action is so the Zetsu 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 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.

Because of their modifications, their DNA is very similar to Hashirama's, as revealed by Shizune and Sakura Haruno's autopsy results, and they are able to use Wood Release, albeit on a weaker scale. However, through Kabuto's experimentation on Yamato, their strength increased to make them presumably more suited for combat with enhanced power. Due to their genetic structure, direct contact with somebody that exudes a powerful life force, such as Naruto in Nine-Tails Chakra Mode, causes them to turn into trees.

In the anime, the White Zetsu Army showed their capability to take on the properties of any nearby material. When located on the battle on the Seventh Front, they took on the characteristics of a special, poisonous, red soil, and were able to 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.

Fourth Shinobi World War: Countdown
After creating an alliance with Kabuto, Tobi leads him underground and shows Kabuto his army of 100,000 White Zetsu in an underwater cavern beneath the Demonic Statue of the Outer Path.

Fourth Shinobi World War: Confrontation
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 had 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 soldiers 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 soldiers 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 Zetsu was found out and stopped by Sakura Haruno. Soon after, along with Sakura and her group believing their enemy's true nature as hybrid clones of Hashirama, the White Zetsu's 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. 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 causes 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 fraud, who was impersonating Hinata who was unconscious at the time, before her teammates kill him.

While Naruto and Killer B confronted several of the White Zetsu Army soldiers 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 soldiers 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 soldiers 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.

Fourth Shinobi World War: Climax
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 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.

Birth of the Ten-Tails' Jinchūriki
As Madara faced off against the tailed beasts, a clone managed to recover the right Rinnegan from where Obito had hidden it. He gives the eye to Madara who also severed his 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, he suggests that Madara instead start with the One-Tail for better efficiency, to which Madara agrees on. He subsequently questioned why Gaara had been fighting to help Shukaku, despite the fact that he was no longer his jinchūriki.

He teases Madara about the time the latter needed to seal the tailed beasts, to which Madara responds the rejects of the failed experiment shouldn't be too loud. He answers that there is nothing to wonder about, because they are known as. Madara asked him about another battle and he reassured Madara that the insides were good. He approached Tobi on top of the giant wood statue, saying that Naruto stubbornly clung to life by nature of being an Uzumaki, but would be dead soon enough, after losing his tailed beast. When the war ended with the Allied Shinobi Forces's victory, Sasuke and Naruto ended the Infinite Tsukuyomi, freeing all the victims of its binding. This also caused the White Zetsu Army to crumble into dust.

Versus Momoshiki Arc
Despite the destruction of the White Zetsu Army, fifteen years after the war, it was revealed that a mutated version of White Zetsu was still at large. When it killed a band of thieves and left the remaining member traumatised from the experience, Konohagakure sent Team 7 to investigate. Inside a mining cave, the White Zetsu attacked the team.

Road to Ninja: Naruto the Movie
Several White Zetsu Army soldiers disguised as the deceased Akatsuki members were sent to attack Konoha at the beginning of the movie, at the behest of Tobi.

Trivia

 * It's unknown what happened to them, but as Tobi was seen disintegrating after the Infinite Tsukuyomi was undone, it's possible that the clones suffered the same fate.