Michael by his refusal to grant them any gifts, Isaac attempted to reconcile with Michael, only to be personally insulted by him, sparking a civil war, which is mentioned by Skylitzes, Psellos, and Attaleiates; Psellos himself led the embassy from Michael to Isaac. Isaac then gathered the support of other military elites before marching for Constantinople. At Constantinople, the Battle of Petroe took place on 20 August 1057, a decisive victory for Isaac, and reportedly one of the bloodiest battles the Byzantines engaged in during a civil war. Isaac's victory placed the military aristocracy firmly back in control and marked the first time a general had held the throne since the death of Emperor Basil II in 1025. Nikephoros led a wing of Isaac's forces during the battle, suggesting he had been a part of Isaac's inner circle; Skylitzes mentions that during this battle Nikephoros fought a duel against one of Michael's mercenaries, Randolf the Frank. In 1059, Isaac placed Nikephoros in command of the Danube frontier, where he remained until 1064. During his time at this command, he saved the life of the future Emperor Romanos IV Diogenes during Isaac's campaign against the Hungarians. Nikephoross narrative picks up once more during the reign of Constantine X Doukas (); in 1061 he was made doux of Thessalonica by Constantine, and ordered to settle complaints in the theme. The first complaint was a dispute centered on the Byzantine government's confiscation of some of the property and Paroikoi (serfs) of the Iveron Monastery of Mount Athos, which the monastery viewed as unlawful. Nikephoros sent Michael the spatharokandidatos to inquire into the case, before ruling that, based upon a chrysobull issued by Basil II which had declared that the monastery's property and Paroikoi were exempt from taxes, they could not be confiscated by the government. Nikephoros settled another dispute in February 1062, this time between the Monastery of Lavra and Theodoros of Aichmalotou, a local landowner, over monastic property; Nikephoros ruled in favor of the monastery. Nikephoros settled a boundary dispute between the Iveron Monastery and the Bishop of Ezoba, basing his ruling on the knowledge of the local populace. The last Thessalonian dispute which Nikephoros ruled on was between the Iveron Monastery and the metochion of Melissourgeion; the metochion appears to have ignored a ruling previously made by Empress Theodora Porphyrogenita, which Nikephoros reasserted. In the fall of 1064, the Oghuz Turks