Danzo Shimura was one of the Konohagakure elders and the rival of Hiruzen Sarutobi, the Third Hokage during since their youth. Danzo handled all of Konohagakure's darker, but necessary operations, albeit at Hiruzen's approval. After the thwarted invasion of Akatsuki's leader, Pain, and Tsunade's incapacitation, Danzo became the official Sixth Hokage Candidate, but he was killed before he could office.
Danzo Shimura was born decades before the start of the series, in an era of constant war. Since their childhood, Danzo was good friends with Hiruzen Sarutobi, but became his rival due to always feeling inferior to him, and strived to surpass him. When they were adults, Danzo and his team, along with Hiruzen and his, were formed into a squad led by Tobirama Senju, and on one their missions, they found themselves pursued by the Kinkaku Strike Squad of Kumogakure. As it was realized that in order for the team to escape, one of them would have to act a diversion, but would also die doing so, Danzo, after internally struggling with his fear of dying, decided to be the sacrifice, but Hiruzen beat him to it. However, Tobirama decided to do it in the end, appointing Hiruzen as the Third Hokage. Angered by this, Danzo began to strive for the title himself, and waited patiently for decades for an opportunity to arise. Taking over all the dark opperations within Konohagakure, at Hiruzen's approval due to his not being able to follow the Second Hokage's legacy, Danzo founded the Anbu faction Root, wherein he personally selected young shinobi with exceptional talent to be members. Though Root was later publically disbanded, Danzo continued to secretly run it in the shadows. During the Second Shinobi World War, Danzo teamed up with Amegakure leader Hanzo to take out Yahiko, the leader and founder of the mercenary organization Akatsuki, believing it would further his progress towards becoming Hokage. However, he was forced to flee after Nagato, Yahiko's friend and a Rinnegan user, killed all of his and Hanzo's men, and Danzo later betrayed Hanzo.
In later years, Danzo began to have dealings with Orochimaru, who once accompanied him to an orphanage where Danzo forced a former member of Root named Nonno to accept an intel mission, also recruiting Kabuto Yakushi, one of the orphans, when he spotted the boy spying. Although both became valuable agents within Root, Nonno and Kabuto eventually proved to be too dangerous to the faction due to their skills, a threat which Danzo attempted to solve by setting Nonna up to kill Kabuto, having deceived her into not recognizing him by use of false photographs, and sent Orochimaru to kill the survivor. Unknown to him, Orochimaru instead took Kabuto under his wing. At the time when the Nine-Tails, Kurama, attacked the village, the Uchiha clan was absent from its defense, causing Danzo to suspect they were behind the attack. He supported relocating them to the outskirts of the village where they could be easily monitored. Only Hiruzen opposed taking these measures, as Danzo was supported by his fellow elders Koharu and Homura. After the Uchiha clan began to plot a coup to take over Konohagakure, Danzo used Itachi Uchiha's pacifist nature to force him to provide him and the others with intel on their actions. When Hiruzen decided to try and end the coup diplomatically, Danzo secretly met with Itachi and forced him to make a deal with him to be able to save his brother, Sasuke Uchiha, by killing off the rest of the clan, or else he woud be considered part of their plot and they would all be killed. Itachi accepted the deal and, after Hiruzen failed to resolve the matter his way, he carried out his end of it. Before leaving on the mission Danzo had given him to protect the village from within the shadows, Itachi threatened him that if he ever harmed Sasuke, he would reveal all that he knew of Danzo and Konohagakure's secrets to their enemies. Unwilling to test Itachi, Danzo never harmed Sasuke.
At the time of the massacre, Danzo also met with Obito Uchiha, posing as Madara Uchiha, for, as of yet, unknown reasons. What happened during this meeting is not currently known. After the massacre, Danzo also gathered ten Sharinagan and embedded them into his right arm, which belonged to Shisui Uchiha, who Danzo robbed of one of eyes to gain the Mangekyo Sharingan and Kotoamatsukami, the strongest genjutsu.
Danzo made his debut in part two of the series in Tsunade's office, where his fellow elders, Koharu and Homura, forced Tsunade to allow one of his men, Sai, to accompany Team Seven to the rendevous point where Sasori, a member of Akatsuki recently killed, was to meet a spy he had within the ranks of Orochimaru, who had Sasuke Uchiha. Danzo had given Sai a mission to killed Sasuke, and a list of Tsunade's bodyguards to convince Orochimaru that the facade Sai would offer, to ally with him, was really the purpose of his presence. However, the mission eventually met with failure, something that disappointed Danzo. He allowed Sai to remain with Team Seven, but reminded him that emotions led to hatred in turn.
During Pain, the leader of Akatsuki's invasion of Konohagakure, Danzo, in the anime, alerted Koharu and Homura to Tsunade's intension to summon back Naruto, and later killed Kosuke( in the manga, he did only this), the messenger toad present, to prevent this from happpening when they only submitted to Tsunade's angry will. Later, he gathered his Root members and told them not to interfere with Pain's efforts against the village, hoping they would end Tsunade's reign, and allow him a chance to become Hokage, maintaining that Tsunade would be able to save most of the villagers when asked. After Naruto arrived and eventually defeated Pain, Danzo took advantage of Tsunade's then incapacitation at a meeting with the Daimyo who, after a brief consideration following a speech by Danzo, appointed him the official Sixth Hokage Candidate.
Upon returning from the meeting with the Daimyo, Danzo received a letter from A, the Fourth Raikage, informing him of the Five Kage Summit and of Sasuke Uchiha's actions in the Land of Lightning. As his first official order, Danzo ordered for Sasuke to be executed and branded him a missing-nin. Though he preferred to have Naruto confined to protect the Nine-Tails, he settled for having him watched by Root agents at all times, being completely aware of his now immense popularity after he defeated Pain, as well as the fact that he would need the support of the Jonin to become the official Hokage. Ordering Anko and some of his men to go and find Kabuto and bring him back, as the latter had medical information that would help with his eye and arm, Danzo departed for the Five Kage Summit with his bodyguards, Torune and Fu, wiping out a squad of wouldbe assassins with aide from his Sharingan in his right eye along the way. After he arrived at the meeting, Danzo's only active part was revealing Obito Uchiha's involvement in the Akatsuki. He used his Mangekyo Sharingan and Kotoamatsukami technique to control Mifune, the moderator and Samurai general, and force him to suggest an alliance between the five Kage and their villages to fight Akatsuki and point him out to be the leader, while pointing out reasons for the others not being suitable. However, he was discovered and exposed by Ao, one of the Fifth Mizukage's bodyguards, but before anything could be done, White Zetsu appeared and revealed the presence of Sasuke Uchiha. After he was seeming dispatched and A left after Sasuke, Mifune reprimanded Danzo for his actions, though he defended them by saying that the shinobi world must become one. After Sasuke eventually arrived, battered and beaten by A, Danzo used the moment to flee with his men, and was pursued by Ao, who they managed to lose.
Later, they were cut off by Obito Uchiha, posing as Madara Uchiha, who Danzo ordered Torune and Fu to distract while he unsealed his arm. They are, however, both easily defeated by Obito, who brought out Sasuke in front of Danzo just as he managed to finish unsealing his arm. Danzo then prepared for battle as he showed them his right arm, embedded with ten Sharingan. As he attacked Sasuke following a question, Danzo was shocked to see Sasuke use Susanoo, and was snatched up by one of its hands. Sasuke asked Danzo again if he had ordered Itachi to wipe out the Uchiha, and Danzo, following torture, confirmed it indirectly. As he lectured Sasuke, Danzo was crushed, but using Izanagi, a dojutsu even the Uchiha forbade use of, Danzo survived and the battle commenced. Any damage done to Danzo continued to have no effect as he kept reappearing. After Sasuke lowered his guard, Danzo used his Wind Release: Vacuum Sphere technique to wound Sasuke, who summoned a giant hawk. As Sasuke charged, Danzo caught him by the throat and placed a paralyzing curse mark on him, before being slashed and having his arm cut off by Sasuke, which did nothing as he reappeared again. Sasuke used Tsukuyomi on Danzo, but he easily broke it because it was too weak, and Sasuke became paralyzed. Deactivating Izanagi, Danzo prepared to finish Sasuke, but before he could, Sasuke unleashed his Susanoo in armored form and broke the curse mark. As Sasuke fired a crossbow at him with Susanoo, Danzo was forced to counter with Wood Release, before he could reactivate Izanagi. Recognizing that he had to keep some power on hand to fight Obito, Danzo summoned his Baku summon, which paralyzed Sasuke's Susanoo with its suction power, allowing Danzo to tear it open from behind.
However, Sasuke thwarted the Baku with Fire Release and repelled Danzo, who contiued to fight him with Wind Release and reappear when hurt completely healed by Iznagai. After he saw he had one eye left, Danzo and Sasuke each created a chakra nature blade and clashed, impalling one another through the chest. With Sasuke mortally wounded, Danzo thought he'd won until Izanagi didn't take effect and it was revealed that the last eye he thought was open was an illusion Sasuke cast on him seconds before. Collapsing, Danzo lost control of Hashirama Senju's cells in his right arm, and was forced to amputate it. As he stood before the now healed Sasuke, Danzo revealed the eleventh Sharingan in his right eye and took Karin, Sasuke assistant, who healed him, hostage to help his new strategy, but Sasuke impaled them both through the chest close to the heart with his Chidori Sharp Spere. Dying, Danzo attempted to flee, but was cut off by both Sasuke and Obito at both sides. Determined not to allow them to live, Danzo activated his Reverse Four Symbols Sealing Technique to drag Sasuke and Obito with him to the grave, lamenting as he experienced death how he could never surpass Hiruzen or become Hokage and how now he would give his own life to protect Konohagakure, just as Hiruzen had done in the past. Though both Obito and Sasuke got out of range, Danzo destroyed Shisui's eye to keep it from Obito.
Danzo was, in his youth, an eager, irascible shinobi prone to outbursts. He was also very loyal to Konohagakure and had some honor and nobility to him, as when he and his squad were surrounded by the Kinkaku Strike Squad, he volunteered to act as a diversion, despite knowing and struggling with his fear of dying as a result. In later years, especially after he founded Root, Danzo lost all of his emotions, believing them to be a weakness and always attempted to make Root members lose their emotions through a very brutal training. Although he was very loyal to konoha, Danzo's own views as to how it should be run differed from those of the Hokage, as in his eyes, the village's safety is top priority over all else, even morals and ethics. As such, he hated the views of all the previous Hokage(though in some ways he carried on Tobirama Senju's legacy in ways only he could), believing them to be the reason for what happened to Konohagakure in recent years. Since their youth, Danzo was good friends with Hiruzen Sarutobi, but always felt beneath him, which caused Danzo to view him as a rival he wanted to surpass. Nevertheless, however, he valued their friendship enough that when he died, Danzo pondered what he mean't to Hiruzen. Danzo was also quite power hungry, shown in his allowing Orochimaru to implant the DNA of Hashirama Senju into him to give him Wood Release and allow him to control the Nine-Tails, which he also stole the Sharingan from Shisui Uchiha(also taking Shisui's right arm after he died) to be able to do, also gaining the ability to use Izanagi through ten other Hsaringan stolen from the rest of the clan after they were massacred. This, he did without grief, despite Shisui's unwavering loyalty to Konohagakure.
Danzo was an immensely powerful and skilled shinobi, easily Kage-level, and was the rival of Hiruzen Sarutobi, the Third Hokage, since their youth. He was easily considered by his fellow elders, Koharu and Homura, to be one of the finest shinobi in Konohagakure in life and was offically made the Sixth Hokage Candidate with little hesitation. Danzo's power was such that he was able to easily and single-handedly slay an entire squad of wouldbe assassins and fight on even terms with Sasuke Uchiha, despite his old age and Sasuke's excessive use of Susanoo, as well as his other Mangekyo Sharingan techniques, in a fight that nearly ended as a stalemate, and that would have if not for the fortunate intervention of Karin, Sasuke's teammate, at the vital moment, who healed Sasuke, putting Danzo at an overwhelming disadvantage. During his battle with Sasuke, Danzo was able to hold back for most of the time to fight with Obito Uchiha, who he believed to be Madara Uchiha, immediately afterwards, all the while not being able to utilize Shisui Uchiha's Mangekyo Sharingan in his right eye.
Due to his old age and lifetime of experience, Danzo's variety of skills were, even when he died, very formidable. Danzo was highly skilled at using Wind Release nature transformation, able to easily utilize very powerful techniques that could equal the strength of and clash with Sasuke's Susanoo with instant ease. Danzo had a unique summoning contract that allowed him to summon the Baku, a tapir-like monster which dwarfed Sasuke's Susanoo in size, and which could use its extreme suction ability to compliment Danzo's Wind Release to the point that he was able to rip open Sasuke's armored Susanoo with one attack. Danzo could fire bullets of wind from his mouth that could smash through stone and, in the anime, showed the ability to use Wind Release and shuriken to create giant buzz saws that could keep their momentum even when countered. Danzo was also very skilled with sealing techniques, able to brand all Root members with seals to prevent them from telling of his actions and employ paralyzing curse marks which could bind someone completely. His strongest sealing technique was his Reverse Four Symbols Sealing Technique, which he cleverly set as a booby trap to activate at his death and drag and seal anyone within range into his corpse. Using this, he caught both Obito and Sasuke Uchiha off-guard, which visibly shocked them. Danzo was also very skilled in using and dispelling genjutsu, even Sasuke's inept Tsukuyomi, which he broke instantly. Despite his old age, Danzo was very strong, fast, and agile, abe to repel Karin with a single kick and cause stone to crumble when she hit it, catch Sasuke Uchiha off-guard by the throat(placing a paralyzing curse mark as he did), and evade the close range attack of Sasuke's Susanoo with a high jump, also showing great reflexes.
Danzo's most fearsome and formidable abilities were the various bodily implants he did to himself or received from Orochimaru. Danzo took the right eye of Shisui Uchiha before he died, and his right arm after he died, replacing his own with each to gain Shisui's Mangekyo Sharingan and the Kotoamatsukami, the strongest genjutsu. After the massacre of the Uchiha clan, Danzo took up to ten Sharingan eyes and implanted them into his right arm. Desiring to be able to control all the eyes, as well as Kurama, the Nine-Tails, Danzo allowed Orochimaru to experiment on him and implant the DNA of Hashirama Senju, the First Hokage, into his right arm as well, allowing him access to both the First's Wood Release kekkei genkai and the forbidden dojutsu Izanagi. Danzo was very skilled at using Shisui's eye, able to instantly locate a squad of shinobi and use the Kotoamatsukami technique with great ease and skill, able to control others without direct sight of them. Danzo power with Wood Release, however, was pale compared to Hashirama himself and he could only use it from his right arm. However, after he was mortally wounded by Sasuke, Danzo lost control over the cells and was forced to amputate his arm, losing his Wood Release. With Izanagi, which Danzo could use from any of his eyes, but chose to do so only from the ones in his arm, Danzo could control reality and illusion about himself, transfering any disadvantages, like fatal wounds, into a dream, while leaving any advantages a part of reality. Aided by Hashirama's cells, Danzo could use Izanagi for one minute an eye at the cost of losing its use afterwards to blindness. Using this to the full effect, Danzo was able to exhaust and mortally wound Sasuke Uchiha at the cost of the same. In order to conserve his chakra, Danzo put a seal on his arm and bandaged his right eye, as all his Sharingan were active. Along with Wood Release, the cells of Hashirama enhanced Danzo's already quite large chakra reseves and let him control ten Sharingan at once.