So begins this effervescent history of an Italy about to shake itself free of the medieval age and move confidently into the Renaissance. First, though, there was an ordeal to pass through, one worthy of the imagination of Dante. Unleashed by a pause in the cataclysmic Hundred Years' War, hordes of soldiers with an appetite for pillage swooped down on the opulent city-states of Italy -- bloated with gold from trade and the birth of the modern banking industry -- and commenced to unburden them of their wealth. The greatest of all the mercenary captains was Sir John Hawkwood, an English expatriate and military genius who formed his own army and cleverly pitted ancient rivals against one another: Florence against Siena, Milan against the papacy -- collecting tribute from them all, holding the Pope for ransom, and setting blood running in the streets. The Devil's Broker is more than a riveting account of fortunes gained and lost by treachery and the sword: it is a lavish portrait of the fourteenth century, which Barbara Tuchman called "calamitous"; the Black Plague that struck down the mighty and the abject with equal ferocity; the violent schism in the Catholic Church that sent the Pope scurrying to Avignon for safety; the religious mania offset by a gargantuan appetite for spectacle, luxury, and self-indulgence. Among the other titans moving through Frances Stonor Saunders's magnificent narrative are the anorexic and power-hungry St. Catherine of Siena, an ill-tempered and comfort-loving Petrarch, and a curious and amused diplomat-spy named Geoffrey Chaucer, who would draw on Hawkwood's career for his own "Knight's Tale."