Cornelius Nepos
Kagan believes that while Alcibiades was a commander of considerable ability, he was no military genius, and his confidence and ambitions went far beyond his skills. He thus was capable of important errors and serious miscalculations. Kagan argues that at Notium, Alcibiades committed a serious error in leaving the fleet in the hands of an inexperienced officer, and that most of the credit for the brilliant victory at Cyzicus must be assigned to Thrasybulus. In this judgement, Kagan agrees with Cornelius Nepos, who said that the Athenians' extravagant opinion of Alcibiades's abilities and valor was his chief misfortune.