[4] Bruno was born circa 1045 in Solero either to nobles or parents of modest means named Andrea and Guglielmina.

[4][1] He spent his theological education in the Benedictine house of Santa Perpetua near his town in Asti and at the University of Bologna where he also studied humanities and the liberal arts.

[5] It was around this time that he wrote one of his earliest works, Expositio in psalterium Gallicanum, dedicated to his bishop, Ingo of Asti (1072-1079).

[14] During May and June 1081, the Emperor-elect Henry IV brought his army and his Clement III (Wibert of Ravenna) to the neighbourhood of Rome, and besieged the city.

King Henry returned at the end of 1082 for a siege of seven months, during which fierce fighting in and around the Leonine City caused Pope Gregory to seek refuge in the Castel Sant' Angelo.

[20] Pope Victor III (1086–1087)[21] named him the Librarian of the Holy Roman Church,[22] and he held the position until he left for Montecassino in 1099.

Bishop Bruno accompanied Pope Urban on his tour of southern Italy, and was present at Salerno on 14 January 1093, where he subscribed a grant of privileges to Abbot Peter of Cava.

Urban held a council at Piacenza during the first week of March, and was gratified and encouraged by the reception he received from every quarter.

Bruno accompanied Urban II to Moyenmoutier, near Tours, where, on 3 March, he was invited to consecrate the capella infirmorum.

[31] In August 1096, the papal suite began its return to Italy, and was in Asti on 9 September; they reached Rome by Christmas.

Bishop Bruno accompanied him, and subscribed a papal privilege for the benefit of Abbot Peter of Cava at Salerno on 30 August 1100.

[33] Bernhard Gigalski argues that it was in the second half of 1102, perhaps between August and December, that Bishop Bruno entered the monastic state at Montecassino.

[36] Peter the Deacon of Montecassino adds that the people of Segni were put out by Bruno's decision, and complained to Pope Paschal.

He undertook a mission to the Kingdom of France along with Prince Bohemond I of Antioch for Pope Paschal II in 1106, and held a council at Poitiers on 25 June 1106.

[43] In the synod he repeated his objections to lay investiture, and he forbade clerics from wearing expensive secular clothes.

[48] On 18 April, at Ponte Mammolo on the Anio River, the cardinals who prisoners along with the pope were compelled to sign the papal promise to observe the agreement which Henry had drawn up.

[50] When the bishops of Lucca and Parma and the ministers of the Camaldolese and Vallombrosian chapters asked his views on investiture as heresy and what the pope was thinking, Bruno imprudently wrote that the pope did not like him and did not consult him; but that he himself continued to follow the policy of Gregory VII and Urban II.

[51] At a council held at the Lateran in March 1112, Paschal was compelled to retract his grant and modify his opinions in the investiture controversy.

[53] Paschal gave another speech justifying his conduct, and Bruno arose to say, "Let us praise God and give Him thanks, because our lord and head repents that he had subscribed to that heresy."

[55] Paschal sent a letter to the monks of Montecassino, ordering them to cease their obedience to Bruno and to proceed to elect a new abbot.

[58] The signing of the Concordat of Worms on 23 September 1122, and its ratification by Pope Calixtus II at the First Lateran Council on 27–30 March 1123, ended the discussion over lay investiture.

[62] It is said that he declined the cardinalate, while other sources suggest he had been made the Cardinal-Bishop of Segni even though the suburbicarian diocese had not existed at that stage.