Danzō Shimura

An elder ninja of Konoha, is a war monger whos politics operated in opposition to Sandaime Hokages politics. Within the ANBU corps, he created and led the training division known as Root, which was detached from the main ANBU. The Root group was disbanded and he lost his position, however many of its old members is still loyal to him. He is still a mjor piece in the power play of Knoha, though with his own influence within the village

Background
In the past, he competed with Sarutobi for the position of Third(Sandaime) Hokage. He created the (now disbanded) ANBU training department known as and acted as its head. Danzo was the one who recommended that Sai be placed in Team Kakashi. He appears to have lost an arm at some point, the cause of which remains unknown, and may have also lost his right eye.

Personality
Danzo is a war monger, who would rather prefere eliminating threats and ordered them executed instead of using negotiations and peacetalks. Albeit not an official part in the affairs of Konoha, he still maintain an eye on everything, and will immidietly act if he sees anything that might look like a threat to Konoha.

Even though he adresses Tsunade verry politly, even calling her princess, he is not pleased with her, mainly because she is the granddaughter of Hashirama Senju the First(Shodaime) Hokage and who has inherited the politics and teachings as him, something that Danzo opposes.

Sai and Sasuke Arc
Despite Danzo's apparent support for the Hokage and Konoha, Tsunade does not trust him; this is apparently well founded, as Danzo had given Sai a secret mission that Tsunade was unaware of: sending Sai to contact Orochimaru and offer to act as a subordinate for him. Yamato believes that Danzo is trying to take over Konoha with Orochimaru's help. This is apparently proven when it is revealed that the envelope Danzo sent Orochimaru was full of pictures and information on the true identities of Konoha's ANBU. However, all of these are nothing more than a front to let Sai get close to Orochimaru, so that Sai can execute his true mission: the assassination of Sasuke Uchiha. After learning of the failed assassination attempt of Sasuke, and Sai's attachment to Team Kakashi, he merely states that "emotion brings hatred, and hatred brings war."

He is also mentioned by Tobi to be one of the three surviving that know "the truth" of Itachi Uchiha.

Speculations
Fans has speculated that Danzo could also be Madara Uchiha, Tobi has bolts on the same arm that Danzo has covered up. Similar hair styles. Not only that, he and Madara share the same hate for the First, Second, and Third Hokage's Teachings and Philosophy. Plus Madara hates the Senju clan, and the first and second were both Senju. Danzo also despises Tsunade for being the Grand-daughter of the First. Danzo also has the same eye covered up that Madara has his Sharingan. Kisame's revelation of Madara being Mizukage offers more support to this theory as Danzo's Root is said to use extremely similar methods to Kirigakure earlier on, the education that led to the village being referred to as the Village in the Bloody Mist.