Concordat of Worms in the context of "Guelphs and Ghibellines"

The Investiture Controversy or Investiture Contest (Latin: Controversia de Investitura, German: Investiturstreit, pronounced [ɪnvɛstiˈtuːɐ̯ˌʃtʁaɪt] ) was a conflict between the Church and the state in medieval Europe over the ability to choose and install bishops (investiture), abbots of monasteries, and the Pope himself. A series of popes in the 11th and 12th centuries undercut the power of the Holy Roman Emperor and other European monarchies, and the controversy led to nearly 50 years of conflict.

It began as a power struggle between Pope Gregory VII and Henry IV (then King, later Holy Roman Emperor) in 1076. The conflict ended in 1122, when Pope Callixtus II and Emperor Henry V agreed on the Concordat of Worms. The agreement required bishops to swear an oath of fealty to the secular monarch, who held authority "by the lance" but left selection to the church. It affirmed the right of the church to invest bishops with sacred authority, symbolized by a ring and staff. In Germany (but not Italy and Burgundy), the Emperor also retained the right to preside over elections of abbots and bishops by church authorities, and to arbitrate disputes. Holy Roman Emperors renounced the right to choose the Pope.

Pope Callixtus II or Callistus II (c. 1065 – 13 December 1124), born Guy of Burgundy, was the head of the Catholic Church and ruler of the Papal States from February 1119 to his death in 1124. His pontificate was shaped by the Investiture Controversy, which he was able to settle through the Concordat of Worms in 1122.

As son of Count William I of Burgundy, Guy was a member of and connected to the highest nobility in Europe. He became archbishop of Vienne and served as papal legate to France. He attended the Lateran Synod of 1112. He was elected pope at Cluny in 1119. The following year, prompted by attacks on Jews, he issued the bull Sicut Judaeis which forbade Christians, on pain of excommunication, from forcing Jews to convert, from harming them, from taking their property, from disturbing the celebration of their festivals, and from interfering with their cemeteries. In March 1123, Calixtus II convened the First Lateran Council which passed several disciplinary decrees, such as those against simony and concubinage among the clergy, and violators of the Truce of God.

Henry V (German: Heinrich V.; probably 11 August 1081 or 1086 – 23 May 1125) was King of Germany (from 1099 to 1125) and Holy Roman Emperor (from 1111 to 1125), as the fourth and last ruler of the Salian dynasty. He was made co-ruler by his father, Henry IV, in 1098.

In Emperor Henry IV's conflicts with the imperial princes and the struggle against the reform papacy during the Investiture Controversy, young Henry V allied himself with the opponents of his father. He forced Henry IV to abdicate on 31 December 1105 and ruled for five years in compliance with the imperial princes. He tried, unsuccessfully, to withdraw the regalia from the bishops. Then in order to at least preserve the previous right to invest, he captured Pope Paschal II and forced him to perform his imperial coronation in 1111. Once crowned emperor, Henry departed from joint rule with the princes and resorted to earlier Salian autocratic rule. After he had failed to increase control over the church, the princes in Saxony and on the Middle and Lower Rhine, in 1121 the imperial princes forced Henry V to consent with the papacy. He surrendered to the demands of the second generation of Gregorian reformers, and in 1122 he and Pope Callixtus II ended the Investiture Controversy in the Concordat of Worms.

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 First Council of the Lateran was the 9th ecumenical council recognised by the Catholic Church. The first ecumenical council to be held in Western Europe and the first since the Great Schism of 1054, it was convoked by Pope Callixtus II in December 1122, immediately after the Concordat of Worms. The council sought to bring an end to the practice of the conferring of ecclesiastical benefices by people who were laymen, free the election of bishops and abbots from secular influence, clarify the separation of spiritual and temporal affairs, re-establish the principle that spiritual authority resides solely in the Church and abolish the claim of the Holy Roman Emperor to influence papal elections.

The council was significant in size: 300 bishops and more than 600 abbots assembled at Rome's Lateran Palace in March 1123, and Callixtus II presided in person. During the council, the decisions of the Concordat of Worms were read and ratified. Various other decisions were promulgated.

The Synod of Verona was held November 1184 under the auspices of Pope Lucius III and the Holy Roman Emperor Frederick I.

The meeting was to address numerous issues. Some of these were the dispute over claims between empire and papacy in central Italy, the proprietary concerns of the bishopric of Gurk, plans for a crusade to the Holy Land, a dispute over the investiture of the rival Archbishops of Trier, Folmar of Karden (the pro-papal candidate) and Rudolf of Wied (afterward invested as anti-archbishop by Barbarossa under the terms of the Concordat of Worms), and the condemnation of heresy. It also addressed the issue of marriage, particularly in response to the condemnation of marriage by the Cathars, finally listing it as a sacrament.