In 1014, Boniface aided the
Emperor Henry II in putting down Margrave
Arduin of Ivrea, who claimed the
Kingdom of Italy in opposition to Henry. His father nominated him as heir over his brothers and, in 1016, he was again fighting alongside the emperor, this time against the
margrave of Turin,
Ulric Manfred II. In 1020, Boniface defeated a rebellion of his brother Conrad, but the two reconciled and both were later recorded as dukes. In 1027, he supported the candidacy of the Salian
Conrad II, Holy Roman Emperor and
King of Germany for the thrones of Italy and the Holy Roman Empire against the other claimants:
William V of Aquitaine,
Robert II of France, or
Hugh Magnus. When Boniface's Lombard enemies tried to incite his brother against him, the two offered battle to them at Coviolo, near Reggio, and emerged victorious, though Conrad was killed. When Conrad II finally succeeded in entering Italy, he was met with defiance at Lucca and he deposed the reigning margrave of Tuscany,
Rainier, and gave his lands and titles to Boniface. This seems to be the probable scenario, though the exact date of Boniface's assumption of the Tuscan lordship is uncertain. He thereby considerably increased his paternal domains and Boniface rose to be the most powerful person between the middle Po and the northern border of the
Patrimonium Petri (
Patrimony of Saint Peter). Emperor Conrad II wanted to tie his most powerful vassal in south of the Alps to his inner circle in the long term through a marriage. Boniface attended the emperor at the city of
Nijmegen in 1036 on the occasion of the wedding of Conrad II's son
Henry with
Gunhilda of Denmark. On that occasion Conrad, his family and his court took up residence in Nijmegen for more than a month. Here Boniface met
Beatrice of Lorraine, niece and foster daughter of Empress
Gisela of Swabia with whom a marriage covenant could be arranged. According to the agreements, Beatrice brought important assets in Lorraine: the Château of
Briey and the Lordships of Stenay,
Mouzay,
Juvigny,
Longlier and
Orval, all the northern part of her paternal family's ancestral lands. As the daughter of Duke
Frederick II of Upper Lorraine and
Matilda of Swabia, she and her sister
Sophia were raised in the imperial court by their aunt Empress Gisela (her mother's sister) after the deaths of their parents. For Boniface, the marriage to Beatrice, a close relative of the Emperor, brought him not only prestige but also the prospect to finally have an heir; his first marriage with
Richilda (died after February 1036), daughter of
Giselbert II,
Count Palatine of
Bergamo, brought one daughter, born and died in 1014. Boniface subdued
Pavia and
Parma, in revolt against the emperor, and the emperor made a treaty with Boniface, an act which has been construed as recognition of Boniface's independence. In 1032, he was at war with the rebel Count
Odo II of Blois. In early summer 1036, In 1037, he helped put down a revolt against the Emperor Conrad, and in February 1038, hosted the Emperor, while the latter journeyed to Florence. In 1043, for services rendered the Empire, he received the
Duchy of Spoleto and
Camerino. He also acquired more land in Parma and
Piacenza, and his chief residence in this time was at Mantua. In 1039, Boniface travelled to
Miroalto to aid Henry against the rebellious Odo of Blois. While he was returning, he destroyed the grain fields of the region and the enraged populace retaliated and stole some of his retainers' horses. It was during his blood reprisal that Boniface made his most famous recorded statement. Preparing to hack off the ears and nose of a young man, Boniface was confronted by the youth's mother, who begged him be spared and promised him her son's weigh in silver. Boniface replied to his offer that he "was no merchant, but a soldier," adding: "Absit ut hostes ferro capti redimantur argento". (Far be it that what was captured by steel should be redeemed with silver.) In 1046, Henry III entered Italy to be crowned emperor. Boniface received the emperor and the empress,
Agnes of Poitou, with honour and munificence on their arrival at Piacenza and his governor did so at
Mantua on their return journey. The relationship between Boniface and Henry, however, soon deteriorated in 1047. ==Papal intrigue==