"Crisis in the Byzantine Empire" may have brought about the First Crusade

Everyone knows that the First Crusade began with a call from Pope Urban II to free Jerusalem from the Muslims. That is, everyone but British historian Peter Frankopan, whose new book, The First Crusade: the Call from the East, offers a different explanation.

Frankopan, who is director of the Centre for Byzantine Research at the University of Oxford, believes that the Crusade was not instigated by the Pope, but was a reaction to a "crisis in the Byzantine Empire" in the second half of the 11th century in which Emperor Alexios Komnenos faced a revolt from the cities of Nicaea and Antioch.