Background
The Norman advances in southern Italy, following the gift of Aversa in 1030, had alarmed the Pope. In 1052 Leo met Henry III, Holy Roman Emperor and his relative, in Saxony and asked for aid in curbing the Normans. Aid was refused and Leo returned to Rome in March 1053 with only around 700 Swabian infantry and levied a force of Italians and Lombardss from the south, he also arranged an alliance with the Byzantines to recapture Siponto (Manfredonia). Leo led his army south and west to Siponto but was intercepted by the Norman force at the bridge over the River Fortore at Civitate in Capitanate, to the northwest of Foggia.
The Battle
The Norman army was smaller than that of the Pope and initially the Norman commanders sought a truce and negotiations. The delegation was dismissed but neither side was willing to fight, the Pope hoped that the Byzantine force under Argyrus would soon arrive, and only after a few days, as their supplies failed, did the Norman force attack. The Pope had around 6,000 men and the Norman force was around 3,500, mostly cavalry.
The Norman army was in three parts; the main body was commanded by Richard, Count of Aversa; the right wing by Humfrey d'Hauteville, Count of Apulia; and the left wing by Robert, the brother of Humphrey (later known as the Guiscard). The Papal army was commanded by Geoffrey, Duke of Lorraine and Rudolph, Prince of Benevento. The Pope observed the battle from Civitate.
The Norman cavalry came down from a hill onto the plain in front of the town. On accepting the initial Norman cavalry charge the majority of the levy fled, leaving only the Swabian infantry to fight to the death.
The Pope was taken prisoner by the victorious Normans. There is some uncertainty over how this happened. Papal sources say that Leo left Civitate and surrendered himself to prevent further bloodshed. Other sources indicate that the inhabitants of Civitate handed the Pope over. He was treated respectfully but was imprisoned at Benevento for almost nine months and forced to ratify a number of treaties favourable to the Normans.