Khalifa Uthman bin Affan - Battle of the Camel

When after the assassination of Uthman, Ali became the Caliph Talha and Zubair took the allegiance to Ali, but soon they repudiated such allegiance and supported the demand for vengeance for the blood of Uthman. Talha, Zubair, and Ayesha occupied Basra and the battle of the Camel was fought between the supporters of Ali, and the supporters of Talha, Zubair, and Ayesha outside Basra. In this battle, Ali won and the cause of Talha and Zubair was lost. Talha escaped from the battlefield, but fell a victim to an arrow shot by Marwan b Hakam. If is reported on the authority of Alqama b Waqas that in Basra, Talha said that he was guilty of a lapse in the matter of his conduct towards Uthman, and he wanted to atone for such lapse by supporting the demand for the vengeance for the blood of Uthman.

Taha Hussain's view
From the accounts that have come down to us, the conduct of Talha appears to be inexplicable. Uthman made some gifts to Talha and Talha supported Uthman. Later Talha joined the rioters, and opposed Uthman. Taha Hussain has expressed the view that as long as Uthman met the demands of Talha, Talha supported him but when Uthman did not or could not meet the demands of Talha, Talha joined the opposition. Talha was an eminent companion of the Holy Prophet, whom the Holy Prophet had given the tidings of paradise. He was one of the six persons whom Umar regarded as his probable successors. We cannot therefore conceive that such an eminent person could be unscrupulous enough to change sides on account of personal motives. It is also inconceivable that such eminent persons like Talha and Zubair should first offer allegiance to Ali and then repudiate it and-resort to war. It appears that all the details relevant to the matter at issue are not available with us, and in the absence of such details it is difficult for us to pass any judgement about the conduct of Talha.