After the Macedonian dynasty, the Empire fell into a period of difficulties due to an outdated military model relying on mercenaries, and a series of threats by new enemies. In southern Italy, the Normans conquered the Byzantine lands and established a Kingdom of Sicily in 1130. In Anatolia the Seljuq Turks advanced and dealt Emperor Romanos IV a crushing defeat in 1071, which enabled them to conquer all of Anatolia.
This complete fragmentation, however, was followed by the last strong Byzantine dynasty; the Komnenids. The five Komnenid Emperors presided over a sustained (but ultimately incomplete) restoration of the military, territory, economy, and political strength of the Byzantine Empire. It was during the Komnenid Emperor Alexios I that the First Crusade was initiated, and John II and Manual I played important parts during the Second Crusade.
After close to a century of rising fortunes, however, the Komnenid dynasty ended in a succession crisis and a popular revolt, after which a combination of gross incompetence and bitter infighting amongst the elite cause Byzantium to permanently lose financial and military supremacy.
This complete fragmentation, however, was followed by the last strong Byzantine dynasty; the Komnenids. The five Komnenid Emperors presided over a sustained (but ultimately incomplete) restoration of the military, territory, economy, and political strength of the Byzantine Empire. It was during the Komnenid Emperor Alexios I that the First Crusade was initiated, and John II and Manual I played important parts during the Second Crusade.
After close to a century of rising fortunes, however, the Komnenid dynasty ended in a succession crisis and a popular revolt, after which a combination of gross incompetence and bitter infighting amongst the elite cause Byzantium to permanently lose financial and military supremacy.

(1)
Romanos IV

An
AE
Follis
struck 1068-1071 A.D.
in
Constantinople
Obverse: IC-XC - Bust of Christ facing with nimbate cross, pallium and colobium, and raising right hand in benediction, scroll in left hand.
Reverse: MP-OV - Facing bust of the Virgin Mary, nimbate and wearing pallium and maphorium.
Diameter:
27.4 mm
Die Orientation: 6 H
Weight: 6.39 g
Die Orientation: 6 H
Weight: 6.39 g
Romanos IV, Class G Anonymous Follis overstruck on a Constantine X Follis.
SB 1854 (Constantine X).