Apulia is an autonomous region in SE Italy. It became a county after the conquest by the Normans in 1042; raised to a dutchy in 1059 by Pope Nicholas II who gave it to Robert Guiscard. It was united with the kingdom of the Two Sicilies in 1130, which is the reason some historians refer to Normans from this area as Sicilians.

Weis' "Ancestral Roots. . ." (103:24). Duke of Apulia, Calabria, & Sicily, 1058; Norman conquerer of Southern Italy.

From Wikipedia:
Robert Guiscard (from Latin Viscardus and Old French Viscart, often rendered the Resourceful, the Cunning, the Wily, or the Fox—most closely related to the archaism wiseacre) (c.1015 – 1085) was the most remarkable of the Norman adventurers who conquered Southern Italy and Sicily. He was count (1057-1059) and then duke (1059-1085) of Apulia and Calabria after his brother Humphrey's death.
From 999 to 1042 the Normans were pure mercenaries, serving either Byzantines or Lombards. Then Sergius IV of Naples, by installing the leader Rainulf Drengot in the fortress of Aversa in 1029, gave them their first base, allowing them to begin an organized conquest of the land.
In 1035 there arrived William Iron-Arm and Drogo, the two eldest sons of Tancred of Hauteville, a petty noble of the Cotentin in Normandy. The two joined in the organized attempt to wrest Apulia from the Greeks, who by 1040 had lost most of that province. In 1042 Melfi was chosen as the Norman capital, and in September of that year the Normans elected as their count William Iron-Arm, who was succeeded in turn by his brothers Drogo, Comes Normannorum totius Apuliae e Calabriae, and Humphrey, who arrived about 1044.
The year 1047 saw the arrival of Robert, the sixth son of Tancred of Hauteville and eldest by his second wife Fressenda. According to the Byzantine historian Anna Comnena, he had left Normandy with only five mounted riders, and thirty followers on foot, and, upon arriving in Langobardia, he became the chief of a roving robber-band. Anna Comnena also leaves a physical description of Robert Guiscard:
This Robert was Norman by descent, of minor origin, in temper tyrannical, in mind most cunning, brave in action, very clever in attacking the wealth and substance of magnates, most obstinate in achievement, for he did not allow any obstacle to prevent his executing his desire. His stature was so lofty that he surpassed even the tallest, his complexion was ruddy, his hair flaxen, his shoulders were broad, his eyes all but emitted sparks of fire, and in frame he was well-built ... this man's cry it is said to have put thousands to flight. Thus equipped by fortune, physique and character, he was naturally indomitable, and subordinate to no one in the world.
Lands were scarce in Apulia at the time and the roving Robert could not expect any grant from Drogo, then reigning, for Humphrey had just received his own county of Lavello. Robert soon joined Prince Pandulf IV of Capua in his ceaseless wars with Prince Guaimar IV of Salerno (1048). The next year, however, Robert left Pandulf, over Pandulf's reneging on a promise of a castle and a daughter's hand, according to Amatus of Montecassino. Robert returned to his brother Drogo and asked for a fief again. This time, Drogo, who had just finished campaigning in Calabria, gave Robert command of the fortress of Scribla. It was, however, a dead-end, and Robert moved to the castle of San Marco Argentano, after which he later named the first Norman castle in Sicily: San Marco d'Alunzio, at the site of ancient Aluntium.
It was during his time in Calabria, that Robert married his first wife, Alberada of Buonalbergo, the aunt of Lord Girard of Buonalbergo. Guiscard soon rose to distinction. The Lombards turned against their erstwhile allies and Pope Leo IX determined to expel the Norman freebooters. The army which he led towards Apulia in 1053 was, however, overthrown at the Battle of Civitate sul Fortore by the Normans, united under Humphrey, who commanded the centre against the Swabians. Count Richard of Aversa, who commanded the right van, early put the Lombards in flight and chased them down before returning to help rout the Swabians. Guiscard had come all the way from Calabria to command the left. His troops were in reserve until, seeing Humphrey's forces ineffectually charging the pope's centre, he called up his father-in-law's reinforcements and joined the fray, distinguishing himself personally, even being dismounted and remounting again three separate times according to William of Apulia.
In 1057, Robert, vindicated by his actions at Civitate, succeeded Humphrey, over his elder half-brother Geoffrey, as count of Apulia and, in company with Roger, his youngest brother, carried on the conquest of Apulia and Calabria, while Richard conquered the principality of Capua. Soon after his succession, probably in 1058, Robert separated from his wife Alberada because they were related within the prohibited degrees to marry Sichelgaita, the daughter of Gisulf II of Salerno, Guaimar's successor. In turn for giving him his sister's hand, Gisulf demanded of Robert that he destroy two castles of his brother William, count of the Principate, which had encroached on Gisulf's territory.
The Papacy, foreseeing the breach with the Holy Roman Emperor (the Investiture Controversy), then resolved to recognize the Normans and secure them as allies. Therefore at the Council of Melfi, on 23 August 1059, Pope Nicholas II invested Robert as duke of Apulia, Calabria, and Sicily, and Richard of Aversa as prince of Capua. Guiscard, now "by the Grace of God and St Peter duke of Apulia and Calabria and, if either aid me, future lord of Sicily", agreed to hold his titles and lands by annual rent of the Holy See and to maintain its cause. In the next twenty years he made an amazing series of conquests, winning his Sicilian dukeship.
At the time of the opening of the Melfitan council in June, Robert had been leading an army in Calabria, the first strong attempt to subjugate that very Greek province since the Iron-Arm's campaigns with Guaimar. After attending the synod for his investiture, he returned to Calabria, where his army was besieging Cariati. After Robert's arrival, Cariati submitted and, before winter was out, Rossano and Gerace also. Only Reggio was left in Greek hands when Robert returned to Apulia. In Apulia, he worked to remove the Byzantine garrisons from Taranto and Brindisi, before, largely in preparation for his planned Sicilian expedition, he returned again to Calabria, where Roger was waiting with siege engines.
The fall of Reggio, after a long and arduous siege, and the subsequent capitulation of Scilla, an island citadel to which the Reggian garrison had fled, opened up the way to Sicily. Roger first led a tiny force to attack Messina but was repulsed easily by the Saracen garrison. The large invading force which could have been expected did not materialize, for Robert was recalled by a new Byzantine army, sent by Constantine X, ravaging Apulia. In January 1061, Melfi itself was under siege and Roger too was recalled. But the full weight of Robert's forces forced the Greeks to retreat and by May Apulia was calm.
Invading Sicily with Roger, the brothers captured Messina (1061) with comparable ease: Roger's men landed unsighted during the night and surprised the Saracen army in the morning. The Guiscard's troops landed unopposed and found Messina abandoned. Robert immediately fortified Messina and allied himself with Ibn at-Timnah, one of the rival emirs of Sicily, against Ibn al-Hawas, another emir. The armies of Robert, his brother, and his Moslem friend marched into central Sicily by way of Rometta, which had remained loyal to al-Timnah. They passed through Frazzanò and the pianura di Maniace, where George Maniakes and the first Hautevilles distinguished themselves twenty-one years prior. Robert assaulted the town of Centuripe, but their resistance was strong, and he moved on. Paternò fell and he brought his army to Enna (then Castrogiovanni), a formidable fortress. The Saracens sallied forth and were defeated, but Enna itself did not fall. Robert turned back, leaving a fortress at San Marco d'Alunzio, named after his first stronghold in Calabria. He returned to Apulia with Sichelgaita for Christmas.
He returned in 1064, but bypassed Enna taking straight for Palermo. Sadly, his campsite was infested with tarantulas and had to be abandoned. The campaign was unsuccessful this time, though a later campaign, in 1072, saw Palermo fall and for the rest of Sicily it was only then a matter of time.
Bari was reduced (April 1071), and the Greeks finally ousted from southern Italy. The territory of Salerno was already Robert's; in December 1076 he took the city, expelling its Lombard prince Gisulf, whose sister Sichelgaita he had married. The Norman attacks on Benevento, a papal fief, alarmed and angered Gregory VII, but pressed hard by the emperor, Henry IV, he turned again to the Normans, and at Ceprano (June 1080) reinvested Robert, securing him also in the southern Abruzzi, but reserving Salerno.
Guiscard's last enterprise was his attack on the Greek Empire, a rallying ground for his rebel vassals. He contemplated seizing the throne of the Basileus and took up the cause of Michael VII, who had been deposed in 1078 and to whose son his daughter had been betrothed. He sailed with 16,000 men against the empire in May 1081, and by February 1082 had occupied Corfu and Durazzo, defeating the Emperor Alexius in front of the latter (Battle of Dyrrhachium, October 1081). He was, however, recalled to the aid of Gregory VII, besieged in Castel Sant'Angelo by Henry IV (June 1083).
Marching north with 36,000 men he entered Rome and forced Henry to retire, but an émeute of the citizens led to a three days' sack of the city (May 1084), after which Guiscard escorted the pope to Rome. His son Bohemund, for a time master of Thessaly, had now lost the Greek conquests. Robert, returning to restore them, occupied Corfu and Kephalonia, but died of fever in the latter on July 15 1085, in his 70th year. He was buried in S. Trinità at Venosa.
Guiscard was succeeded by Roger Borsa, his son by Sichelgaita; Bohemund, his son by an earlier Norman wife Alberada, being set aside. He left two younger sons: Guy, Duke of Amalfi, and Robert Scalio, neither of whom made any trouble for their elder brothers.
At his death Robert was duke of Apulia and Calabria, prince of Salerno and suzerain of Sicily. His successes had been due not only to his great qualities but to the "entente" with the Papal See. He created and enforced a strong ducal power which, however, was met by many baronial revolts, one being in 1078, when he demanded from the Apulian vassals an "aid" on the betrothal of his daughter. In conquering such wide territories he had little time to organize them internally. In the history of the Norman kingdom of Italy Guiscard remains essentially the hero and founder, as his nephew Roger II is the statesman and organizer.
In The Divine Comedy, Dante Alighieri sees the spirit of Robert Guiscard in the Heaven of Mars with the other noteworthy crusaders.