The papal election held from 4 to 7 September 1159 following the death of Pope Adrian IV resulted in the election of two rival popes. A majority of the cardinals elected Cardinal Rolando of Siena as Pope Alexander III, but a minority refused to recognize him and elected their own candidate, Ottaviano de Monticelli, who took the name Victor IV, creating a schism that lasted until 1178.

The schism was a result of the growing tensions inside the Sacred College of Cardinals concerning the foreign policy of the Holy See. The Papal States in the 12th century were a buffer between the Holy Roman Empire and the Norman Kingdom of Sicily. After the Concordat of Worms in 1122, the Papacy allied with the Empire rather than with the Normans, but during the pontificate of Adrian IV (1154–59) this alliance broke up because Emperor Frederick I Barbarossa did not fulfil the terms of the treaty of Constance (1153) that obliged him to help the Papacy to restore its authority in Rome and in other territories controlled by the king of Sicily. In these circumstances Adrian IV decided to break the alliance with the Emperor and to make peace with William I of Sicily by signing the Treaty of Benevento (1156). In the following years there were growing tensions between the papacy and Emperor Frederick I Barbarossa (e.g. a dispute at the diet of Besançon in 1157). Frederick tried – with significant success – to strengthen his influence on the Church in Germany. The change of direction of the papal foreign policy resulted in the division of the Sacred College into supporters and opponents of the new policy, who were unable to achieve a compromise after the death of Adrian IV.

The election of 1159 had also significant legal consequences. Up to that time, the election of the new pope required unanimity among the electors, which led to the schism when the existence of factions in the Sacred College made the unanimity impossible. To avoid such schism in the future, the Third Lateran Council in 1179 promulgated the decree Licet de evitanda discordia, which established the rule that the Pope is elected with a majority of two thirds of the cardinals participating in the election.

Pope Adrian IV died on 1 September 1159. Fearing a possible schism, shortly before his death he recommended to the cardinals the election of Cardinal Bernard of Porto as his successor.

There were thirty-one cardinals in September 1159. One of them seems not to have participated in the election, leaving thirty electors:

Elector	Faction	Cardinalatial title	Elevated	Elevator	Notes
Imar, O.S.B. Cluny	Imperial	Bishop of Tusculum	13 March 1142	Innocent II	Dean of the Sacred College of Cardinals
Gregorio della Suburra	Sicilian	Bishop of Sabina	1 March 1140	Innocent II	Sub-dean of the Sacred College of Cardinals
Ubaldo Allucingoli	Sicilian	Bishop of Ostia e Velletri	16 December 1138	Innocent II	Future Pope Lucius III (1181–85)
Giulio	neutral	Bishop of Palestrina	19 May 1144	Lucius II
Bernard, Can.Reg.	Sicilian	Bishop of Porto e Santa Rufina	22 December 1144	Lucius II	Archpriest of the Vatican Basilica; designated by Adrian IV but not elected
Walter, Can.Reg.	Sicilian	Bishop of Albano	19 December 1158	Adrian IV
Ubaldo Caccianemici, Can.Reg.	Sicilian	Priest of S. Croce in Gerusalemme	19 May 1144	Lucius II	Protopriest of the Sacred College of Cardinals; Cardinal-nephew (?)
Ottaviano de Monticelli	Imperial	Priest of S. Cecilia	25 February 1138	Innocent II	Elected Antipope Victor IV
Astaldo degli Astalli	neutral	Priest of S. Prisca	17 December 1143	Celestine II
Guido di Crema	Imperial	Priest of S. Maria in Trastevere	21 September 1145	Eugenius III	Future Antipope Paschal III (1164–68)
Rolando	Sicilian	Priest of S. Marco and Chancellor of the Holy Roman Church	22 September 1150	Eugenius III	Elected Pope Alexander III
Giovanni Gaderisio, Can.Reg.	Sicilian	Priest of S. Anastasia	22 September 1150	Eugenius III
Giovanni da Sutri	neutral	Priest of SS. Giovanni e Paolo	21 February 1152	Eugenius III
Enrico Moricotti, O.Cist.	neutral	Priest of SS. Nereo ed Achilleo	21 February 1152	Eugenius III
Giovanni Morrone	Imperial	Priest of SS. Silvestro e Martino	23 May 1152	Eugenius III
Ildebrando Grassi, Can.Reg.	Sicilian	Priest of SS. XII Apostoli	23 May 1152	Eugenius III
Bonadies de Bonadie	neutral	Priest of S. Crisogono	21 December 1156	Adrian IV
Alberto di Morra, Can.Reg.Praem.	neutral	Priest of S. Lorenzo in Lucina	21 December 1156	Adrian IV	Future Pope Gregory VIII (1187)
Guglielmo Marengo, O.Cist.	Imperial (?)	Priest of S. Pietro in Vincoli	14 March 1158	Adrian IV
Odone Bonecase	Sicilian	Deacon of S. Giorgio in Velabro	4 March 1132	Innocent II	Protodeacon of the Sacred College of Cardinals
Rodolfo	neutral	Deacon of S. Lucia in Septisolio	17 December 1143	Celestine II
Giacinto Bobone	neutral	Deacon of S. Maria in Cosmedin	22 December 1144	Lucius II	Future Pope Celestine III (1191–98)
Ottone da Brescia	Sicilian	Deacon of S. Nicola in Carcere	21 February 1152	Eugenius III
Ardicio Rivoltella	Sicilian	Deacon of S. Teodoro	21 December 1156	Adrian IV
Boso, Can.Reg.	Sicilian	Deacon of SS. Cosma e Damiano	21 December 1156	Adrian IV	Camerlengo of the Holy Roman Church; prefect of the Castle Sant’Angelo
Simeone Borelli, O.S.B.Cas.	Imperial	Deacon of S. Maria in Domnica	ca.1157	Adrian IV	Abbot of Subiaco
Cinthius Capellus	Imperial (?)	Deacon of S. Adriano	14 March 1158	Adrian IV	nephew of Innocent II
Pietro di Miso	Sicilian	Deacon of S. Eustachio	14 March 1158	Adrian IV
Raymond de Nimes	Imperial	Deacon of S. Maria in Via Lata	14 March 1158	Adrian IV
Giovanni Conti da Anagni	neutral	Deacon of S. Maria in Portico	19 December 1158	Adrian IV

Five electors were created by Pope Innocent II, two by Pope Celestine II, four by Pope Lucius II, eight by Pope Eugenius III and eleven by Pope Adrian IV.

Elector	Faction	Cardinalatial title	Elevated	Elevator	Notes
Rainaldo di Collemezzo, O.S.B.Cas.	neutral	Priest of SS. Marcellino e Pietro	ca.1139–1141	Innocent II	Abbot of Montecassino (external cardinal)

The College of Cardinals was divided into two factions: the so-called "Sicilian" party and the Imperial faction. The "Sicilian" party, led by chancellor Rolando of Siena and Camerlengo Boso, supported the pro-Sicilian policy of Adrian IV. The Imperial faction was led by Ottaviano of S. Cecilia.

It is known that the "Sicilian" party counted thirteen cardinals. They were chancellor Roland of S. Marco, camerlengo Boso of SS. Cosma e Damiano, cardinal-bishops Bernard of Porto, Ubaldo of Ostia, Walter of Albano and Gregorio of Sabina, as well as cardinals Odone of S. Giorgio, Ubaldo of S. Croce, Ottone of S. Nicola, Ardicio of S. Teodoro, Giovanni of S. Anastasia, Ildebrando of SS. Apostoli and Pietro of S. Eustachio.

The Imperial party may have counted as many as nine cardinals, but only six can be identified as its members: Ottaviano of S. Cecilia, Giovanni of SS. Silvestro e Martino, Guido of S. Maria in Trastevere, Imar of Tusculum, Raymond of S. Maria in Via Lata and Simeone of S. Maria in Domnica Guglielmo of S. Pietro in Vincoli was probably the seventh one. Perhaps Cardinal Cinzio of S. Adriano also belonged to this faction. The remaining ten cardinals were neutral.

It is believed that both factions made some preparations to the election in the last months of the pontificate of Adrian IV, although these attempts are known only from the hostile accounts produced for the polemical purposes during the subsequent schism and it is impossible to verify their accuracy. Both sides accused each other of illegal conspiracies. The adherents of Victor IV accused "Sicilians" of receiving the bribes from the king William I of Sicily and the anti-Imperial cities of Brescia, Milan and Piacenza. They ostensibly made an oath not to vote for any candidate outside their circle. On the other hand, "Sicilians" accused imperialists of hatching a plot with the imperial envoy Otto von Wittelsbach, who was present at Rome at the time of the election and gave the significant support to Victor IV in taking control over the Patrimony of St. Peter. It is known that the secular adherents of Cardinal Ottaviano de Monticelli, who was related to the powerful family of the counts of Tusculum, were prepared for the armed confrontation in Rome. Evidently, neither party was prepared for compromise.

The cardinals assembled in the Vatican Basilica on 4 September, three days after the death of Adrian IV. They had decided that, according to the custom, the election should be unanimous to be valid. It seems that the candidature of Bernard of Porto, recommended by Adrian as acceptable for both factions, had never been even advanced. Both parties put forward candidates mutually unacceptable: the imperial party proposed Ottaviano de Monticelli, while "Sicilians" proposed chancellor Rolando. The cardinals discussed for three days without achieving a compromise. However, the "Sicilian" party was able to join all the neutral cardinals and probably detached also some members of the imperial faction. On the fourth day (7 September), Cardinal Rolando of Siena was proclaimed pope by them and took the name Alexander III, although the unanimity had not been achieved and some cardinals still opposed his candidature. According to the manifest of Alexandrine party of October 1159 and an account of Cardinal Boso, on that day Rolando received the votes of all cardinals assembled except three: those of Ottaviano of S. Cecilia, Giovanni of SS. Silvestro e Martino and Guido of S. Maria in Trastevere. Then supporters of Rolando recognized that “It seemed inappropriate that ... the apostolic see ... should remain any longer without a ruler because of the contentiousness of the aforesaid [three] men”. On the other hand, the opposite party claimed that Ottaviano had still nine votes, and that the "Sicilian" party, having majority, simply broke the rule that required unanimity for the valid election. However, the version of the imperial cardinals is believed to be less reliable than the version of the Alexandrine party, even if the latter may be also not fully accurate; based on the subscriptions of the manifests of both parties issued shortly after the election, it is possible to assume that at least twenty-three electors voted for Rolando, and no more than six opposed him.

The electors of Cardinal Rolando, immediately after proclaiming him Pope, attempted to place upon him the purple mantle which symbolized the assumption of the papal office, but then the election entered the tumultuous stage. Cardinal Ottaviano Monticelli snatched the mantle from Alexander's back and his armed bands burst into the basilica. Alexander III and his supporters fled to the citadel of St. Peter, which was in the hands of Cardinal Boso. In their absence, the few cardinals who remained in basilica elected Ottaviano of S. Cecilia to the papacy and enthroned him as Victor IV. The exact number of his electors is not known, but there are good reasons to believe that it was six, including Ottaviano himself, since only five cardinals signed the manifest in his favour in the following month. However, it is possible that some additional cardinals participated in the election of Victor IV but very quickly joined the obedience of Alexander III.

Pope Alexander III remained in the citadel for a week until he was rescued and escorted from Rome by Odo Frangipane, and on September 18 he was eventually bestowed with the purple mantle. On 20 September at the small village of Ninfa, south-east of Velletri, he was consecrated bishop of Rome by Cardinal Ubaldo Allucingoli, bishop of Ostia e Velletri, and crowned by Cardinal Odone Bonecase, protodeacon of S. Giorgio in Velabro. On 27 September he excommunicated Victor IV and his adherents.

Victor IV was consecrated on 4 October in the abbey of Farfa by Cardinal-Bishop Imar of Tusculum, dean of the Sacred College of Cardinals, assisted by the bishops Ubaldo of Ferentino and Riccardo of Melfi. With the armed assistance of Otto von Wittelsbach and his own armed groups in relatively short time he took control over the City of Rome and the Patrimony of St. Peter, while Alexander III took refuge in the territory of the Kingdom of Sicily, and later in France.

Both rivals together with their adherents defended the legality of their elections. In October 1159 cardinals of both obediences produced the manifests to the Emperor Frederick in favour of their elects. The “Alexandrine” manifest was subscribed by twenty three cardinals, while that of Victorine faction only by five. Supporters of Victor IV, admitting that they were in minority, justified their action by the fact that the opposite faction broke the rule of unanimity and – in consequence – the election of Rolando was invalid. The opposite party claimed that the principle of unanimity had been breached by the obstructive conduct of merely three cardinals of the Imperial faction, who stubbornly refused to recognize the candidate desired by the rest of the Sacred College.

Obedience of Alexander III

Obedience of Victor IV

1. Gregorio della Suburra, bishop of Sabina 2. Ubaldo Allucingoli, bishop of Ostia e Velletri 3. Giulio, bishop of Palestrina 4. Bernard, Can.Reg., bishop of Porto e S. Rufina and archpriest of the Vatican Basilica 5. Walter, Can.Reg., bishop of Albano 6. Ubaldo Caccianemici, Can.Reg., protopriest of S. Croce in Gerusalemme 7. Rainaldo di Collemezzo, O.S.B.Cas., priest of SS. Marcellino e Pietro and abbot of Montecassino 8. Astaldo degli Astalli, priest of S. Prisca 9. Giovanni da Sutri, priest of SS. Giovanni e Paolo 10. Errico Moricotti, O.Cist., priest of SS. Nereo ed Achilleo 11. Ildebrando Grassi, Can.Reg., priest of SS. XII Apostoli 12. Giovanni Gaderisio, Can.Reg., priest of S. Anastasia 13. Bonadies de Bonadie, priest of S. Crisogono 14. Alberto di Morra, Can.Reg., priest of S. Lorenzo in Lucina 15. Guglielmo Marengo, priest of S. Pietro in Vincoli 16. Odone Bonecase, protodeacon of S. Giorgio in Velabro 17. Rodolfo, deacon of S. Lucia in Septisolio 18. Giacinto Bobone, deacon of S. Maria in Cosmedin 19. Ottone da Brescia, deacon of S. Nicola in Carcere 20. Ardicio Rivoltella, deacon of S. Teodoro 21. Boso, Can.Reg., deacon of SS. Cosma e Damiano 22. Cinzio Capellus, deacon of S. Adriano 23. Pietro di Miso, deacon of S. Eustachio 24. Giovanni Conti da Anagni, deacon of S. Maria in Portico

1. Imar, O.S.B.Cluny, bishop of Tusculum 2. Guido di Crema, priest of S. Maria in Trastevere 3. Giovanni Morrone, priest of SS. Silvestro e Martino 4. Raymond de Nimes, deacon of S. Maria in Via Lata 5. Simeone Borelli, O.S.B.Cas., deacon of S. Maria in Domnica and abbot of Subiaco

Simeone Borelli joined the obedience of Alexander III already at the end of 1159. Raymond of S. Maria in Vi Lata did the same between February and April 1160. Besides, at the end of 1159 Victor IV created at least three new cardinal-deacons: Bernard of SS. Sergio e Bacco, Giovanni of S Maria in Aquiro and Lando of S. Angelo, while Alexander III appointed on February 18, 1160, cardinal-deacon Milo of S. Maria in Aquiro.

Both popes sent their legates to the Catholic kingdoms in order to secure their recognition. At the council of Pavia in February 1160 Emperor Frederick I declared himself in favour of Victor IV, and the episcopate of the Empire followed him, with the significant exception of archbishop of Salzburg Eberhard I von Hilpolstein-Biburg and his suffragans. King Valdemar I of Denmark also gave his support to Victor IV, but the primate of Denmark archbishop Eskil of Lund became partisan of Alexander III. It seems that Poland also supported Victor IV. The rest of Europe, namely France, England, Spain, Sweden, Norway, Scotland, Hungary, Sicily and the Latin territories in Outremer, recognized Alexander III as true Pope, even if in some of these countries there were a significant Victorine minorities in episcopates or among feudal rulers. The papal schism in Europe was now a fact.

The unity of the Church had been restored only after eighteen years, when Emperor Frederick I Barbarossa and Pope Alexander III signed a Treaty of Venice (1 August 1177); shortly thereafter the pro-imperial pope Callistus III (successor of Victor IV) abandoned his claims to the papacy and submitted to Alexander III (29 August 1178). Victor IV and his successors Paschal III (1164–68) and Callistus III (1168–78) are now regarded as antipopes by the Catholic Church, while Alexander III is recognized as legitimate successor of St. Peter the Apostle.

The election of 1159 and the subsequent schism showed the necessity of amending the rules concerning papal elections. The decree Licet de evitanda discordia issued by the Third Lateran Council in 1179 abolished the rule of unanimity in favour of the rule of the majority of two thirds. The decree confirmed also that all three orders of the College of Cardinals (bishops, priests and deacons) are equal in the papal elections. Although the practice allowing the participation of cardinal-priests and cardinal-deacons on equal rights with cardinal-bishops had been introduced no later than in the papal election, 1118, the decree In Nomine Domini (1059) conferring the special electoral rights on the cardinal-bishops had never been formally revoked up to that time.

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