During this period, the Normans easily imposed their authority over much of southern Italy. An early success was the capture of Conversano, twenty miles south-east of Bari in 1054 though generally the Normans were content to exact tribute from the more strongly defended Apulian towns like Bari, Trani, Otranto and Acerenza. After Leo’s death Humphrey occupied Benevento in the north but, though he besieged the city he was unable to capture it. Capua, concerned by Norman attacks on Benevento restored Pandulf III in January 1056.
In the years after Civitate, there were important changes in Norman attitudes towards Salerno, whose prince had been their main local ally. Formal links may have ended in 1047 but relations remained good under Drogo and the Normans had been responsible for Gisulf II’s installation as prince in 1051-2. However, after 1054 relations became increasingly strained. Humphrey and his half-brother William attacked the principality when Gisulf failed to provide the necessary tribute. The result was the creation of the county of the Principate in 1055 that was held by William and his descendents. The ability of the Salernitans to respond to this aggression was hampered by the growing internal weakness of Salerno. Relations between prince Gisulf and his uncle Guido of Sorrento became very strained: Amatus blamed Gisulf’s poor attitude compared with his uncle’s selflessness but then Amatus consistently sought to blacken Gisulf’s name and thus to justify the eventual conquest of Salerno by Robert Guiscard.
The most spectacular advances were made by Robert Guiscard in the south, finally conquering Calabria with the taking of Reggio in 1060. By 1056, he had taken several of the more important places in northern Calabria: Bisignano, Martirano and Cosenza though he probably only held the region north of the Val di Crati. After his brother Humphrey’s death in early 1057, Guiscard succeeded him as overall leader of the Apulian Normans and this further enhanced his military strength. He also had the help of his youngest brother Roger who had arrived in Italy at about this time. In the late spring or early summer of 1057, Robert and probably Roger advanced as far as Squillace, half-way down Calabria where the peninsula is at its narrowest and then across to Reggio, the capital of Byzantine Calabria at its extreme tip. On his return from ths essentially reconnaissance expedition, Nicastro and Maida, town on the south-west edge of the Sila Mountains submitted to him. At this point, Robert had to return to Apulia to deal with a challenge from his old rival County Peter son of Amicus. In his absence, Roger forced the inhabitants of the Val di Saline in central Calabria into submission and fortified a base near Nicefora. Robert returned in the autumn of 1057 (though the chronology is far from certain) and launched a more serious attack on Reggio.but poor planning forced a retreat. However, his determination to bring Calabria under his control is clear in his remaining at Maida over the winter of 1057-8.
In early 1058, however, Robert and Roger fell out largely because the latter did not consider he had received a far share of the gains in Calabria. Malattera’s account is the only source for this disagreement and is very partial towards Roger suggesting that Robert was being thoroughly unreasonable. He also suggests some jealousy on Robert’s part of Roger’s growing military reputation. There are certain problems with accepting Malaterra’s account at face-value. Guiscard was facing opposition in Apulia and his control over Calabria was limited to the western side of northern and central Calabria. There was not a great deal of land that Robert with which to endow his brother. Nor was it clear that Robert had the manpower to garrison all the settlements in the region under his control. Norman tactics appear to have been to establish a fortified base and then terrorise the other settlements into submission paying tribute and giving hostages but not necessarily under direct Norman control. Robert was also reluctant to dilute his own property and powerbase in Calabria even in favour of his brother largely becase his fellow Normans and especially the ‘sons of Amicus’ kin group resented his authority in Apulia. Control of Calabria gave him a degree of personal security.
In addition, the spring of 1058 saw a serious famine in parts of Calabria caused partly by the Norman attacks and partly by a prolonged drought. Malattera’s account is graphic and not exaggerated. Guiscard’s problems in Apulia, his dispute with Roger and his marriage to Sichelgaita of Salerno in the second half of 1058, prevented further advance in Calabria. Given these circumstance, it is not surprising that Robert gave way in his dispute with Roger and promised to give him half of Calabria (the southern half that was as yet unconquered). He did give Roger the base at Mileta and from here Roger advanced aggressively south in early 1059 crushing a counter-attack by the governor of Gerace and the bishop of Cassano. In late 1059, or more probably early 1060 Guiscard brought substantial reinforcements and the two brothers besieged and captured Reggio and Squillace. Calabria was now more or less under Norman control.
Why did Calabria fall under Norman control so quickly in the late 1050s? This can be attributed to a number of factors. First, the defenders lacked outside support. There were still contacts between Byzantine Calabria and Constantinople in the 1050s but the internal problems in the empire and attacks from the Pechenegs and the Turks meant there was only minimal military support available for Italy. There were few attempts to fight the Normans in the open and the one attempt in 1059 ended disastrously. Secondly, Norman tactics, made essential by the limited number of troops available to them before 1060 secured the surrender of towns and strongpoints by destroying the crops of the inhabitants. These were especially effective given the mountainous nature of Calabria where cultivatable land was in short supply. Finally, the Normans also allowed remarkable lenient terms for surrender. In central Calabria, the local Greek patriciate was left in place. Garrisons were introduced into key locations from the start but in less sensitive areas the process was slower: Cosenza, for example, did not have a Norman garrison until 1091. Tribute in return for peace was a price worth paying for many Calabrians.
Other conquests were also underway. In June 1058, Richard of Aversa captured Capua. He displaced the old Lombard princely family and usurped their title and authority. He was now in a position to extend his rule away from the restricted territory around Aversa and over the whole principality. His new status was recognised by his reception at Montecassino by the new abbot Desiderius in November 1058 and increasingly he was seen as the protector of the monastery. He had, in a word, become respectable.
The final legitimisation of both Richard of Capua and Robert Guiscard came with their recognition by the Papacy. In the latter months of 1058 Robert married Sichelgaita, the sister of Gisulf II of Salerno. He repudiated his first wife Alberada on the grounds of consanguinity. This is generally regarded as an excuse to enable Robert to enter into a marriage that was politically expedient and provided a degree of acceptance in the eyes of the Lombards as well as the Normans. It benefited Salerno as Robert now provided protection against the aggression of Richard of Capua on the northern borders of the principality. What made Guiscard’s marriage different from previous Lombard-Norman marriages was that he was the first to marry a legitimate daughter of an actual prince. When he eventually conquered Salerno in 1076, this gave him and more especially Roger Borsa, his son by Sichelgaita a claim to rule they would otherwise not have had.
After Humphrey’s death in 1057, Robert Guiscard initiated a plan to consolidate Norman power in southern Italy, in order to frustrate the Byzantines and the vague autonomous threats of the Norman barons. Although powerful, he felt he needed to show that his pursuit of conquest was allied with a moral authority. There was little chance that the German Empire would look favourably at his project during the minority of Emperor Henry IV. The authority of the German emperors had never been welcomed in Mezzogiorno. Robert sought help from the papacy, thinking that despite Civitate in 1053, the time was right for a compromise. Fortunately political circumstances were favourable at this time. Pope Victor II (1055-7) and Stephen IX (1057-8) were not well disposed towards the Normans; both had been closely associated with Leo IX’s project in 1053. However, on Stephen’s death in March 1058, the Romans chose one pope (Benedict X) and the reformers another (Nicholas II). Nicholas was quickly established in Rome but he needed support to retain his position. In the spring of 1059, Richard of Capua was persuaded to send 300 knights to support Nicholas and captured his rival to the papal throne. The project was actively supported by the diplomacy of the abbot of Montecassino, Desiderius, who became Pope Victor III, in 1086.
At the synod of Melfi, in 1059, Pope Nicholas II invested Guiscard with the title of duke as well as confirming his right to his possessions in Apulia and Calabria. Furthermore, Sicily under the domination of the Muslims was promised to the Normans, who were assigned to seize it and retain it under the authority of the Holy See. Richard of Aversa was recognised as prince of Capua by the Pope. This was a decisive turning point for Norman authority in southern Italy from now on their legitimacy could not be questioned.
 This should not be ignored as the reason for the repudiation. Amatus suggested (a little time afterwards) that Robert had become increasingly conscious of the sinfulness of the union. It is also possible that the clerical reform movement, established in 1046, was making some headway in southern Italy especially in its objective of improving the morality of the laity. The enforcement of Church’s rules on marriage was part of this process. Despite this, Alberada and Guiscard remained on relatively good terms and their son Bohemond was later to join his father in the attacks on the Byzantine Empire.