Most often called Saruman the White, Saruman was the first of the five Wizards to arrive in Middle-earth, at the end of the first millennium of the Third Age. He was said to be the eldest of the order, and Gandalf acknowledged him as the chief of the Istari.
For a thousand years, and maybe more, he journeyed in the East of Middle-earth, and was little heard of in the West. He had returned, though, by III 2463, for he was present at the foundation of the Council of the Wise, and was made their chief although Elrond and Galadriel would have preferred Gandalf to take this position). It was at about this time that Saruman began to study the Rings of Power, their history and the means of their making.
In III 2759 , he was given the keys of Orthanc by Steward Beren of Minas Tirith, and took up his abode there. He continued his researches into ring-lore, and the making of devices, and was accustomed to watch the stars from the pinnacle of the Tower. He visited Minas Tirith to research the history of the Rings, and found among the ancient books and scrolls the story of the death of Isildur and the loss of the Ruling Ring.
In III 2851, the Council discovered proof that the Necromancer of Dol Guldur was indeed Sauron returned. Many of the Wise wished to attack the fortress and drive Sauron out, but Saruman spoke against this, and dissuaded the Council from mounting an assault. It was only after ninety years had passed that he relented and aided the Council in assailing Dol Guldur, driving Sauron back into Mordor. Saruman's knowledge was vital in this victory, as Gandalf said - 'it was by the devices of Saruman that we drove him from Dol Guldur'.
When the Council debated the Rings of Power, Saruman claimed that his researches showed that the One Ring had been lost forever. It was later shown that he did not believe this, however, and was searching for it himself, having secretly rebelled against the Council.
In July III 3018, when he was ready to reveal himself, Saruman set a trap for Gandalf, using the Wizard Radagast to lure him to Orthanc. When Gandalf came, Saruman revealed that he had made a Ring of his own, and that he was no longer Saruman the White, but claimed the title Saruman of Many Colours. When Gandalf refused to join him, he was imprisoned on the pinnacle of the Tower of Orthanc -- Saruman hoped to gain the secret of the One Ring from him, or at least prevent Gandalf from using it himself.
Encyclopedia of Arda