Bishop of Florence, Italy.
Chosen 155th pope in Siena where the cardinals had fled after the nobles who supported anti-popeJohn Mincius had occupied Rome.
Immediately after his election, Nicholas gathered his army, marched on Rome, and claimed his rightful position.
He was a strong proponent of papal reform.
In 1059 he issued the Papal Election Decree to minimize political interference in papal elections by requiring the pope to be elected only by the college of cardinals.
Favored the elimination of simony, clerical marriage, and lay influence in the Church.
Negotiated a peace with the Normans that ended fighting in Sicily.
Tried to restore a common life for cathedral clergy and to eliminate abuse of ecclesiastical property.