Battle of Parma The Battle of Parma was fought on February 18 , 1248 between the forces of Holy Roman Emperor Frederick II and the Guelphs . The Guelphs attacked the Imperial camp when Frederick II was away . The Imperial forces were defeated and much of Frederick ' s treasure was lost . Background . The free commune of Parma had been a longtime supporter of the Ghibelline ( pro - imperial ) party . However , it was also considered an important stronghold to take by the Guelphs ( pro - papal ) , due to its flourishing economy and its position across the Via Francigena . On 25 June 1243 Innocent IV , who had several friends in the city and had held several positions in the local diocese , was elected as pope . He thus started a plan to bring Parma to the Guelph side , by replacing the current bishop with Alberto Sanvitale , who was more loyal to him , and order the local Franciscans to convince the population to change side . The already strained relationship between emperor Frederick II and the pope worsened : the situation was further aggravated by the coup by which the city fell in the hands of a Guelph group , including Ugo Sanvitale ( the brother of the new bishop of Parma ) and Bernardo di Rolando Rossi ( the pope ' s brother - in - law and a former collaborator of Frederick ) . The emperor knew of the rebellion when he was at Pavia . He immediately mustered an army , marched against Parma from Emilia , ousted Rolando Rossi and installed Tebaldo Franceschi at the new city ' s captain . Innocent IV , however , continued his hate campaign against Frederick both in Lombardy and the Kingdom of Sicily with letters to the local nobility and clergymen . Several noblemen , including the Sanseverino and three Fasanella , set a plot against the emperor in 1244 : however , they were betrayed by a participant , and many were arrested and executed . Some conspirators sought the protection of the pope , who , in the meantime , had moved to Lyon , which was more distant from the imperial armies . Here he summoned the Council of Lyon in 1245 , where it was decided to confirm the excommunication of the emperor , proclaimed in 1227 by Gregory IX . Battle . Now that the papal participation in the plot against him had become clear , Frederick wrote to the noblemen to inform them of the pope ' s vile behavior , and marched with an army to Lyon in 1247 . Once he had arrived in Turin , however , he received news that Parma had rebelled again . According to Salimbene di Adam , a group of Guelph Parmigian refugees who had taken shelter in Piacenza led by Ugo di Sanvitale ( the brother of the new bishop of Parma ) and Bernardo di Rolando Rossi ( the pope ' s brother - in - law and a former collaborator of Frederick ) . They defeated the imperial garrison under the imperial " podestà " Enrico Testa near Borghetto di Taro and occupied the city with no resistance , since the garrison of Enzio of Sardinia , Frederick ' s son , was besieging Quinzano . Frederick immediately diverted his troops to Emilia , and at the same time he called for reinforces from friendly lords and communes . The imperial army was also joined by Enzio , who raised the siege of Quinzano , and by a Cremonese contingent led by Ezzelino III da Romano , as well as by soldiers from Padua , Verona and Vicenza . The pope did his best to send help to Parma from cities faithful to him , such as Milan , Piacenza , Mantua and Ferrara . Gregorio di Montelongo was able to reach the city , organizing its defense with Bernardo Rossi and Gilberto da Gente . Perhaps due to a shortage of siege weapons , Frederick decided to take the city by starvation . The Guelphs were however determined to resist thanks to the papal help , and the siege dragged for eight months . Frederick ordered the construction of an entrenched camp near Grola , calling it " Victoria " ( Latin for " victory " ) , which should include a houses , palaces and a church , declaring that it would be come the seat of his kingdom after the fall of Parma . However , several noblemen abandoned him . Further , on 12 February 1248 Gregorio di Montelongo launched a sortie : Frederick was hunting in the Taro valley , and Vittoria was destroyed . He took refuge at Borgo San Donnino , and then moved to the faithful Cremona . Aftermath . The defeat of Parma was a decisive defeat for Frederick , who had to abandon forever any dream to conquer northern Italy . The Second Lombard League recovered some territories , the whole Emilia and Romagna embraced the Guelph cause , while the Marquisate of Montferrat and the Republic of Genoa remained hostile to him . Ezzelino III , despite remaining in the Ghibelline side , ousted the imperial governor from Monselice . According to anti - imperial Franciscan chronicler Salimbene di Adam , " Parma fuit causa totius ruine " ( " Parma was the cause of the whole ruin " ) .