The Norman offensive at Montemaggiore is led by William Iron Arm, who has been elected the leader of the Normans.

Also present are William's two younger brothers, Drogo and Humphrey.

The Norman contingent had gained considerable strength following the previous battle at Olivento, as new Lombard auxiliaries and Norman mercenaries from Salerno and Aversa, led by Rainulf Drengot, have bolstered their ranks.

The Lombard-Norman army is said to have included two thousand Norman knights, considered an inflated number by modern historians, in addition to Lombard infantry and heavy cavalry formations.

Historian Richard Humble has put the army's numbers at seven hundred Norman knights and about thirteen hundred foot soldiers, roughly double the number estimated by Gordon S. Brown for the preceding battle, in Olivento.

The imperial catepan, Michael Doukeianos, meets the Normans with a numerically greater army.

His army is claimed to have included eighteen thousand men in the Bari Annals (Annales barenses), but estimated by Brown as "several thousand" (at Olivento).

The army is divided into two lines, and consists of fresh troops from Asia and returning soldiers from Sicily.

The imperial forces also include the Norse-dominated Varangian Guard, led by the future Norwegian king Harald Hardrada, and is morally bolstered by the presence of two Greek Rite bishops from Troia and Ofanto.

The Normans attack the imperial army in a spearhead formation, which leads the first line to be driven into the second, and in turn causing confusion among the Greeks.

William suffers from fever and initially watches the fight from a hill, but eventually joins the battle as he is overcome with excitement.

A great number of imperial soldiers, including the two bishops, drown in the Ofanto attempting to flee.

A particularly great number of Varangians also fall in battle, and the imperial troops are eventually defeated.

The Norman victory has been attributed in particular to the addition of the Norman heavy cavalry.

The victory at Montemaggiore provides the Normans with their first significant acquisition of war booty, including military equipment, horses, tents, precious fabrics, as well as gold and silver vessels.

The enrichment of the soldiers in turn attracts more knights to join the rebellion.

With the imperial army crushed, …

Political disturbances continue to plague Campania and …

…Apulia, though they are southern Italy's most flourishing regions.

These regions continue to attract hordes of fortune-seeking Norman immigrants, who are to transform the political role of both regions in the following decades.

The Normans, who had first fought for Constantinople against the Muslims in Sicily, now fight in alliance with the Lombards in Apulia against the Empire.

As more Normans arrive, they carve out small principalities for themselves from their former employers.

Among the most remarkable of these Norman adventurers are the sons of Tancred de Hauteville.

The eldest, William (“Iron Arm”) de Hauteville, having successfully defeated the Greeks who controlled this region for Constantinople, is elected count of Apulia in 104 and assigned Melfi.

Humphrey, the younger brother of William (“Iron Arm”) de Hauteville, has fought since 1035 in Sicily and Apulia; he becomes count of Lavello in 1045.

William “Iron Arm” de Hauteville, Norman lord of Apulia, had been succeeded in 1046 by his younger brother Drogo, whose thirty-two-year-old half brother, Robert Guiscard, joins him in Apulia the following year.

Norman adventurers in the second decade of the eleventh century had begun a prolonged and haphazard migration to southern Italy and Sicily, where they served the local nobility as mercenaries fighting the Arabs and the Empire.

As more Normans arrived, they had carved out small principalities for themselves from their former employers.

Among the most remarkable of these Norman adventurers are the sons of Tancred de Hauteville, who establish their rule over the southern Italian regions of Puglia (Apulia) and …

…Calabria in the 1050s.

Robert Guiscard, sent by his older brothers to Calabria to attack imperial territory, begins his campaign by pillaging the countryside and ransoming its people.

Humphrey of Hauteville, as count of Apulia, had married the sister of the Lombard prince Guaimar IV of Salerno in 1051.

Gisulf, the eldest son and successor of Guaimar and Gemma, daughter of the Capuan count Laidulf, had been made co-prince with his father in 1042 while very young.

Only a decade later, on June 3, 1052, his father is assassinated in the harbor of his capital by four brothers of his wife Gemma, sons of Pandulf V of Capua, who had been goaded into the act by the pro-imperial partisans of Amalfi.

Guaimar's brother Pandulf of Capaccio is also killed, but Guy of Sorrento escapes while Guaimar's sister and niece are locked up.

The brothers-in-law seize the city and elect Pandulf, eldest among them, prince.

Young Gisulf is taken captive by the assassins, but soon his uncle Guy garners a Norman army under Humphrey of Hauteville and besieges Salerno.

The assassins' families soon fall into their enemies' hands and they negotiate their release by releasing Gisulf to Guy.

Guy accepts their surrender soon after, promising not to harm them.

The Normans, however, who maintain they are not bound by Guy's oath, massacre the four brothers and thirty-six others, one for each stab wound found in Guaimar's body.

Thus the Normans show their loyalty to Guaimar even after his death.

The city soon surrenders and Guy and the Normans pay homage to Gisulf, who confirms their titles and lands.

The rocky start to his reign us merely an indication of its character, for Gisulf will hold a grudge against the Amalfitans who had initiated the slaying of his father.

He also, for reasons unknown, will also come to hate the Normans as barbarians and will spend his entire reign in opposition to them.

Pope Leo had joined the Emperor at Pressburg in 1052, and vainly sought to secure the submission of the Hungarians.

At Regensburg, Bamberg and Worms, the papal presence had been celebrated with various ecclesiastical solemnities.

The Normans, who have plundered and devastated many churches and monasteries in their marauding expeditions, continue to present considerable dangers to the existence of the papal state.

The Norman advances in southern Italy had alarmed the papacy for many years, though the impetus for the imminent battle itself has come about for several reasons.

First, the Norman presence in Italy is more than just a case of upsetting the power balance, for many of the Italian locals do not take kindly to the Norman raiding and wish to respond in kind, regarding them as little better than brigands.

The raiding activities which brought about such hatred also occur in the see of Benevento, a deed not emphasized in the Norman chronicles, but for Pope Leo this is the more significant concern in the political instability of the region.

In fact, according to Graham Loud, the Beneventians, who previously had been approached by both the German Emperor Henry III and by the Pope previously to swear fealty, had finally appealed and submitted to Leo to personally take over the control of the city (as well as lifting a previous excommunication) in 1051.

At this point, Benevento is also the border and march land between Rome and the German Empire and the newly established Norman holdings.

The second reason behind the conflict is the instability brought about on the Norman side by the death of Drogo de Hauteville, who had been the nominal war leader of the Normans and Count of Apulia, and who had been murdered in 1051 in unclear circumstances.

According to Malaterra's account, the native Lombards were responsible for the plot, and a courtier named Rito committed the deed at the castrum of Montillaro.

Despite the benefit the pope and both Greek and German emperors would have drawn from his murder, it is difficult to speculate beyond Malaterra's report since the details of the murder do not appear in most other sources, particularly the Norman chronicles.

Nevertheless, there had certainly been a strong reaction to Drogo's death, with his brother Humphrey taking over the leadership position of his brother, and scouring the countryside and his enemies in response.

Finally, in 1052, Leo asks the emperor for aid in curbing the growing Norman power.

The emperor had initially refused to grant the Pope substantial aid against the Normans, in southern Italy, and Leo returns to Rome in March 1053 with only seven hundred Swabian infantry.

Others are also worried about the Norman power, in particular the Italian and Lombard rulers in the south.

The Prince of Benevento, Rudolf, the Duke of Gaeta, the Counts of Aquino and Teano, the Archbishop and the citizens of Amalfi—together with Lombards from Apulia, Molise, Campania, Abruzzo and Latium—answer the call of the Pope, and form a coalition that moves against the Normans.

However, while these forces include troops from almost every great Italian magnate, they do not include forces from the Prince of Salerno, who has more to gain than the others from a Norman defeat.

The Pope had also another friendly power in the Empire ruled by Constantine IX.

At first, the imperial authorities, established in Apulia, had tried to buy off the Normans and press them into service within their own largely mercenary army; since the Normans are famous for their avarice.

To this end, the imperial commander, the Lombard Catepan of Italy Argyrus, had offered money to disperse as mercenaries to the Eastern frontiers of the Empire, but the Normans had rejected the proposal, explicitly stating that their aim is the conquest of southern Italy.

Thus spurned, Argyrus had contacted the Pope, and when, after a fourth Easter synod in 1053, Leo and his army of Italians and Swabian mercenaries move from Rome to Apulia to engage the Normans in battle, an imperial army personally led by Argyrus moves from Apulia with the same plan, catching the Normans in a pinch.