The Council of Piacenza was a mixed synod of ecclesiastics and laymen of the Roman Catholic Church, which took place from March 1 to March 5, 1095, at Piacenza.
The Council was held at the end of Pope Urban II's tour of Italy and France, which he made to reassert his authority after the investiture controversy with Henry IV, Holy Roman Emperor. Two hundred bishops attended, as well as 4000 other church officials, and 30,000 laymen; there were so many people that the council had to be held outside of the city. The massive number of attendees reflects the increased authority of the church in the wake of Pope Gregory VII.
Among the lay attendees was Eupraxia of Kiev, a daughter of Vsevolod I, Prince of Kiev, and sister to his son Vladimir II Monomakh, prince of Kievan Rus. She met with Pope Urban II, and on his urgings Eupraxia made a public confession before the church council. She accused Henry of holding her against her will, forcing her to participate in orgies, offering her to his son Conrad, and of attempting a black mass on her naked body.[1] Those accusations were confirmed in turn by Conrad, who stated that this was the reason he turned against his father.
Also in attendance were ambassadors from Philip I of France, who came to appeal Philip's recent excommunication over his illegal divorce and remarriage to Bertrade de Montfort: Philip was given until Pentecost to rectify his situation. The rest of the business of the council expressed fairly typical church concerns: there were at least 15 canons published during the council, including a condemnation of the Berengerian heresy; a condemnation of the Nicolaitan heresy; an affirmation of the presence of Christ in the Eucharist; denunciations of the Antipope Clement III and his supporters; and a prohibition of payment to priests for baptisms, burials, or confirmations.
In hindsight, the most important attendees were the ambassadors sent by Byzantine emperor Alexius I Comnenus. Alexius had been excommunicated by Gregory VII, and been through a series of reinstatements in the Church, but Urban had ultimately lifted the excommunication when he became pope in 1088, and relations between the east and west were at least temporarily friendly. The Byzantine Empire had lost much of its territory in Asia Minor to the Seljuk Turks in the aftermath of the Battle of Manzikert in 1071, and Alexius hoped western knights could help him restore it.
The ambassadors probably exaggerated the immediate danger to the empire, which was temporarily stalled by Seljuk infighting; Alexius also told them to remind them that Jerusalem was also held by Muslims, knowing that western Christians, too, attached a special significance to the city at the centre of the world which Muslims had denied them pilgrimage to.
Alexius' request was taken far more seriously than he had hoped. Urban may already have been thinking about a crusade to the east, and the request was interpreted as a sign of weakness in both the Eastern empire and the Orthodox church. It has been suggested that Urban may have hoped that by sending help he could also reunite the churches under his authority; however, Urban II never refers to the idea of reuniting the churches under his authority in any of his four extant letters on crusading. News of the threat to the empire and the supposed threat to Jerusalem spread throughout France after the council ended; in November of 1095, Urban called an even bigger council, the Council of Clermont, where the organization of the First Crusade was formally announced.
Most of the information about the Council of Piacenza comes from the chronicler Bernold of Constance, who was probably there himself, as well as Ekkehard of Aura and Guibert of Nogent. No extant contemporary Byzantine sources felt the ambassadors were important enough to mention, although many Byzantine sources from this time no longer exist. For example, the council is mentioned by the 13th century chronicler Theodore Scutariotes, who quotes now-lost contemporary works.