section_path: History/Nicaea to East–West Schism (325–1054)/Middle Ages
section_name: Middle Ages
paragraph_text: Middle Ages
  
  After the fall of the Western Roman Empire, the pope served as a source of authority and continuity. Pope Gregory I (c. 540–604) administered the church with strict reform. From an ancient senatorial family, Gregory worked with the stern judgement and discipline typical of ancient Roman rule. Theologically, he represents the shift from the classical to the medieval outlook; his popular writings are full of dramatic miracles, potent relics, demons, angels, ghosts, and the approaching end of the world.
  
  Gregory's successors were largely dominated by the exarch of Ravenna, the Byzantine emperor 's representative in the Italian Peninsula. These humiliations, the weakening of the Byzantine Empire in the face of the Muslim conquests, and the inability of the emperor to protect the papal estates against the Lombards, made Pope Stephen II turn from Emperor Constantine V. He appealed to the Franks to protect his lands. Pepin the Short subdued the Lombards and donated Italian land to the papacy. When Pope Leo III crowned Charlemagne (800) as emperor, he established the precedent that, in Western Europe, no man would be emperor without being crowned by a pope.
  
  The low point of the papacy was 867–1049. This period includes the Saeculum obscurum, the Crescentii era, and the Tusculan Papacy. The papacy came under the control of vying political factions. Popes were variously imprisoned, starved, killed, and deposed by force. The Counts of Tusculum made and unmade popes for fifty years. Pope John XII, the great-grandson of one such count, held orgies of debauchery in the Lateran Palace. Emperor Otto I had John accused in an ecclesiastical court, which deposed him and elected a layman as Pope Leo VIII. John mutilated the Imperial representatives in Rome and had himself reinstated as pope. Conflict between the Emperor and the papacy continued, and eventually dukes in league with the emperor were buying bishops and popes almost openly.
  
  In 1049, Leo IX travelled to the major cities of Europe to deal with the church's moral problems firsthand, notably simony and clerical marriage and concubinage. With his long journey, he restored the prestige of the papacy in Northern Europe. From the 7th century, it became common for European monarchies and nobility to found churches and perform investiture or deposition of clergy in their states and fiefdoms, their personal interests causing corruption among the clergy. This practice had become common in part because the prelates and secular rulers were also often participants in public life.
  
  To combat this, and other practices that had been seen as corrupting, between the years 900 and 1050, centres emerged promoting ecclesiastical reform, the most important being the Abbey of Cluny, which spread its ideals throughout Europe. This reform movement gained strength with the election of Pope Gregory VII in 1073, who adopted a series of measures in the movement known as the Gregorian Reform, in order to fight strongly against simony and the abuse of civil power and try to restore ecclesiastical discipline, including clerical celibacy.
  
  In 1122, this conflict between popes and secular autocratic rulers such as the Holy Roman Emperor Henry IV and King Henry I of England, known as the Investiture controversy, was resolved by the Concordat of Worms, in which Pope Callixtus II decreed that clerics were to be invested by clerical leaders, and temporal rulers by lay investiture. Soon after, Pope Alexander III began reforms that would lead to the establishment of canon law.
  
  Starting at the beginning of the 7th century, Islamic conquests had succeeded in controlling much of the southern Mediterranean. This was perceived as a threat to Christianity. In 1095, the Byzantine emperor, Alexios I Komnenos, asked for military aid from Pope Urban II in the ongoing Byzantine–Seljuq wars. Urban, at the council of Clermont, called the First Crusade to assist the Byzantine Empire to regain the old Christian territories, especially Jerusalem.
  
  After the fall of the Western Roman Empire, the pope served as a source of authority and continuity. Pope Gregory I (c. 540–604) administered the church with strict reform. From an ancient senatorial family, Gregory worked with the stern judgement and discipline typical of ancient Roman rule. Theologically, he represents the shift from the classical to the medieval outlook; his popular writings are full of dramatic miracles, potent relics, demons, angels, ghosts, and the approaching end of the world.
  
  Gregory's successors were largely dominated by the exarch of Ravenna, the Byzantine emperor 's representative in the Italian Peninsula. These humiliations, the weakening of the Byzantine Empire in the face of the Muslim conquests, and the inability of the emperor to protect the papal estates against the Lombards, made Pope Stephen II turn from Emperor Constantine V. He appealed to the Franks to protect his lands. Pepin the Short subdued the Lombards and donated Italian land to the papacy. When Pope Leo III crowned Charlemagne (800) as emperor, he established the precedent that, in Western Europe, no man would be emperor without being crowned by a pope.
  
  The low point of the papacy was 867–1049. This period includes the Saeculum obscurum, the Crescentii era, and the Tusculan Papacy. The papacy came under the control of vying political factions. Popes were variously imprisoned, starved, killed, and deposed by force. The Counts of Tusculum made and unmade popes for fifty years. Pope John XII, the great-grandson of one such count, held orgies of debauchery in the Lateran Palace. Emperor Otto I had John accused in an ecclesiastical court, which deposed him and elected a layman as Pope Leo VIII. John mutilated the Imperial representatives in Rome and had himself reinstated as pope. Conflict between the Emperor and the papacy continued, and eventually dukes in league with the emperor were buying bishops and popes almost openly.
  
  In 1049, Leo IX travelled to the major cities of Europe to deal with the church's moral problems firsthand, notably simony and clerical marriage and concubinage. With his long journey, he restored the prestige of the papacy in Northern Europe. From the 7th century, it became common for European monarchies and nobility to found churches and perform investiture or deposition of clergy in their states and fiefdoms, their personal interests causing corruption among the clergy. This practice had become common in part because the prelates and secular rulers were also often participants in public life.
  
  To combat this, and other practices that had been seen as corrupting, between the years 900 and 1050, centres emerged promoting ecclesiastical reform, the most important being the Abbey of Cluny, which spread its ideals throughout Europe. This reform movement gained strength with the election of Pope Gregory VII in 1073, who adopted a series of measures in the movement known as the Gregorian Reform, in order to fight strongly against simony and the abuse of civil power and try to restore ecclesiastical discipline, including clerical celibacy.
  
  In 1122, this conflict between popes and secular autocratic rulers such as the Holy Roman Emperor Henry IV and King Henry I of England, known as the Investiture controversy, was resolved by the Concordat of Worms, in which Pope Callixtus II decreed that clerics were to be invested by clerical leaders, and temporal rulers by lay investiture. Soon after, Pope Alexander III began reforms that would lead to the establishment of canon law.
  
  Starting at the beginning of the 7th century, Islamic conquests had succeeded in controlling much of the southern Mediterranean. This was perceived as a threat to Christianity. In 1095, the Byzantine emperor, Alexios I Komnenos, asked for military aid from Pope Urban II in the ongoing Byzantine–Seljuq wars. Urban, at the council of Clermont, called the First Crusade to assist the Byzantine Empire to regain the old Christian territories, especially Jerusalem.