Robert Guiscard in the context of Duchy of Apulia

The Palatine Chapel /ˈpælətaɪn ˈtʃæpəl/ (Italian: Cappella Palatina) is the royal chapel of the Norman Palace in Palermo, Sicily. This building is a mixture of Byzantine, Norman and Fatimid architectural styles, showing the tricultural state of Sicily during the 12th century after Roger I and Robert Guiscard conquered the island.

Also referred to as a Palace church or Palace chapel, it was commissioned by Roger II of Sicily in 1132 to be built upon an older chapel (now the crypt) constructed around 1080. It took eight years to build, receiving a royal charter the same year, with the mosaics being only partially finished by 1143. The sanctuary, dedicated to Saint Peter, is reminiscent of a domed basilica. It has three apses, as is usual in Byzantine architecture, with six pointed arches (three on each side of the central nave) resting on recycled classical columns. The muqarnas ceiling of the nave and the chapel's rectilinear form show the Fatimid influence in the building's construction.

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.

The Principality of Taranto (Latin: Principatum Tarentinum) was a state in southern Italy created in 1088 for Bohemond I, eldest son of Robert Guiscard, as part of the peace between him and his younger brother Roger Borsa after a dispute over the succession to the Duchy of Apulia.

Taranto became the capital of the principality, which covered almost all of the heel of Apulia. During its subsequent 377 years of history, it was sometimes a powerful and almost independent feudal fief of the Kingdom of Sicily (and later of Naples), sometimes only a title, often given to the heir to the crown or to the husband of a reigning queen. When the House of Anjou was divided, Taranto fell to the house of Durazzo (1394–1463).

Roger I (Italian: Ruggero; Arabic: رُجار, romanized: Rujār; Maltese: Ruġġieru; Norse: Rogeirr; c. 1031 – 22 June 1101), nicknamed "Roger Bosso" and "Grand Count Roger", was a Norman nobleman who became the first Grand Count of Sicily from 1071 to 1101.

As a member of the House of Hauteville, he participated in several military expeditions against the Emirate of Sicily (beginning in 1061). He was later invested with part of Sicily by his brother, Robert Guiscard, Duke of Apulia, in 1071. By 1090, he had conquered the entire island. In 1091, he conquered Malta. The state he created was merged with the Duchy of Apulia in 1127 and became the Kingdom of Sicily in 1130. His descendants in the male line continued to rule Sicily down to 1194.

The County of Apulia and Calabria (Latin: Comitatus Apuliae et Calabriae), later the Duchy of Apulia and Calabria (Latin: Ducatus Apuliae et Calabriae), was a Norman state founded by William of Hauteville in 1043, composed of the territories of Gargano, Capitanata, Apulia, Vulture, and most of Campania. It became a duchy when Robert Guiscard was raised to the rank of duke by Pope Nicholas II in 1059.

The duchy was disestablished in 1130, when the last duke of Apulia and Calabria, Roger II, became King of Sicily. The title of duke was thereafter used intermittently as a title for the heir apparent to the Kingdom of Sicily.

The Komnenian restoration (1081–1185) is the term used by historians to describe the military, financial, and territorial recovery of the Byzantine Empire under the Komnenian dynasty, from the accession of Alexios I Komnenos in 1081 to the death of Andronikos I Komnenos in 1185. At the onset of the reign of Alexios I, the empire was reeling from its defeat by the Seljuk Turks at the Battle of Manzikert in 1071. The empire was also being threatened by the Normans of Robert Guiscard, who were invading the Balkans from their base in southern Italy. All this occurred as the empire's military institution was in disarray and had grown increasingly reliant on mercenaries. Previous emperors had also squandered the large gold deposits of Constantinople, so the defense of the empire had broken down, and there were few troops to fill the gaps.

The Komnenoi nevertheless managed to reassert Byzantine pre-eminence in the Mediterranean world, militarily and culturally. Relations between the Byzantine East and Western Europe flourished, epitomized by the collaboration of Alexios I and later emperors with the Crusaders (Alexios was instrumental in calling the First Crusade). The scattered and disorganized Byzantine army was restructured into a competent fighting force that became known as the Komnenian Byzantine army. Although the empire rapidly disintegrated after the death of the last Komnenos emperor, Andronikos I, in 1185, the Komnenian Restoration represented the final apex of the fifteen-hundred year history of the Roman Empire.