Henry IV, Holy Roman Emperor in the context of "Matilda of Tuscany"

The history of Italy in the Middle Ages can be roughly defined as the time between the collapse of the Western Roman Empire and the Italian Renaissance. Late antiquity in Italy lingered on into the 7th century under the Ostrogothic Kingdom and the Byzantine Empire under the Justinian dynasty, the Byzantine Papacy until the mid 8th century. The "Middle Ages" proper begin as the Byzantine Empire was weakening under the pressure of the Muslim conquests, and most of the Exarchate of Ravenna finally fell under Lombard rule in 751. From this period, former states that were part of the Exarchate and were not conquered by the Lombard Kingdom, such as the Duchy of Naples, became de facto independent states, having less and less interference from the Eastern Roman Empire.

Lombard rule ended with the invasion of Charlemagne in 773, who established the Kingdom of Italy and the Papal States in large parts of Northern and Central Italy. This set the precedent for the main political conflict in Italy over the following centuries, between the Pope and the Holy Roman Emperor, culminating with conflict between Pope Gregory VII and Henry IV and the latter's "Walk to Canossa" in 1077.

The Investiture Controversy or Investiture Contest (Latin: Controversia de Investitura, German: Investiturstreit, pronounced [ɪnvɛstiˈtuːɐ̯ˌʃtʁaɪt] ) was a conflict between the Church and the state in medieval Europe over the ability to choose and install bishops (investiture), abbots of monasteries, and the Pope himself. A series of popes in the 11th and 12th centuries undercut the power of the Holy Roman Emperor and other European monarchies, and the controversy led to nearly 50 years of conflict.

It began as a power struggle between Pope Gregory VII and Henry IV (then King, later Holy Roman Emperor) in 1076. The conflict ended in 1122, when Pope Callixtus II and Emperor Henry V agreed on the Concordat of Worms. The agreement required bishops to swear an oath of fealty to the secular monarch, who held authority "by the lance" but left selection to the church. It affirmed the right of the church to invest bishops with sacred authority, symbolized by a ring and staff. In Germany (but not Italy and Burgundy), the Emperor also retained the right to preside over elections of abbots and bishops by church authorities, and to arbitrate disputes. Holy Roman Emperors renounced the right to choose the Pope.

The Road to Canossa or Humiliation of Canossa (Italian: L'umiliazione di Canossa), or, sometimes, the Walk to Canossa (German: Gang nach Canossa/Kanossa) was the journey of the Holy Roman Emperor Henry IV to Canossa Castle in 1077, and his subsequent ritual submission there to Pope Gregory VII. It took place during the Investiture controversy and involved the Emperor seeking absolution and the revocation of his excommunication by the Pope who had been staying at the castle as the guest of Margravine Matilda of Tuscany.

According to contemporary sources, he was forced to supplicate on his knees, waiting for three days and nights before the castle gate while a blizzard raged, "one of the most dramatic moments of the Middle Ages". The episode has spurred much debate among medieval chroniclers as well as modern historians, who dispute whether the walk was a humiliating defeat for the emperor or a "brilliant masterstroke".

In the Middle Ages, the term universal power referred to the Holy Roman Emperor and the Pope. Both were struggling for the so-called dominium mundi, or world dominion, in terms of political and spiritual supremacy.

The universal powers continued into the early 19th century until the Napoleonic Wars. The reshaping of Europe meant the effective end of the Empire. Although the Papacy had its territorial limits confined to the Vatican, it retained its soft power in the contemporary world.

Alexios I Komnenos (Greek: Ἀλέξιος Κομνηνός, romanized: Aléxios Komnēnós, c. 1057 – 15 August 1118), Latinized as Alexius I Comnenus, was Byzantine emperor from 1081 to 1118. After usurping the throne he was faced with a collapsing empire and constant warfare throughout his reign. Alexios was able to curb the Byzantine decline and begin the military, financial, and territorial recovery known as the Komnenian restoration. His appeals to Western Europe for help against the Seljuk Turks were the catalyst that sparked the First Crusade. Although he was not the first emperor of the Komnenian dynasty, it was during his reign that the Komnenos family came to full power and initiated a hereditary succession to the throne.

The son of John Komnenos and a nephew of Isaac I Komnenos, Alexios served with distinction under three Byzantine emperors. In 1081, he led a rebellion against Emperor Nikephoros III Botaneiates and took the throne for himself. He immediately faced an invasion of the western Balkans by the Normans under Robert Guiscard and his son Bohemond. Despite initial defeats, Alexios secured an alliance with Holy Roman Emperor Henry IV and drove back the Normans, recovering most of Byzantine losses by 1085. In 1091, he achieved a decisive victory over the Pechenegs at the Battle of Levounion in Thrace with the help of Cuman allies.