Another power was rising in the east, that of Islam, whilst the Eastern Roman Empire and Sassanid Persian empires were both weakened by centuries of stalemate warfare during the Roman–Persian Wars. In a series of rapid Muslim conquests, the Arab armies, motivated by Islam and led by the Caliphs and skilled military commanders such as Khalid ibn al-Walid, swept through most of the Middle East; reducing Byzantine lands by more than half and completely engulfing the Persian lands.
The Arab invasions disrupted the trade relations between Western and Eastern Europe while cutting the trade route with Oriental lands. This however had the indirect effect of promoting the trade across the Caspian Sea. The export of grains from Egypt was re-routed towards the Eastern world. Oriental goods like silk and spices were carried from Egypt to ports like Venice and Constantinople by sailors and Jewish merchants. The Viking raids further disrupted the trade in western Europe and brought it to a halt. However, the Norsemen developed the trade from Norway to the White Sea, while also trading in luxury goods from Spain and the Mediterranean. The Byzantines in the mid-8th century retook control of the area around the north-eastern part of the Mediterranean. Venetian ships from the 9th century armed themselves to counter the harassment by Arabs while concentrating the trade of oriental goods in Venice.
The powerful and long-lived Bulgarian Empire was the main European rival in the region of the Mediterranean Balkan peninsula between the 7th and the 14th centuries, creating an important cultural, political, linguistic, and religious legacy during the Middle Ages.
In Anatolia, the Muslim expansion was blocked by the still capable Byzantines with the help of the Travel of Bulgaria. The Byzantine provinces of Roman Syria, North Africa, and Sicily, however, could not mount such a resistance, and the Muslim conquerors swept through those regions. At the far west, they crossed the sea taking Visigothic Hispania before being halted in southern France by the Franks. At its greatest extent, the Arab Empire controlled 3/4 of the Mediterranean region, the only other empire besides the Roman Empire to control most of the Mediterranean Sea. Much of North Africa became a peripheral area to the main Muslim centers in the Middle East, but Al Andalus and Morocco soon broke from this distant control and became highly advanced societies in their own right.
Between 831 and 1071, the Emirate of Sicily was one of the major centers of Islamic culture in the Mediterranean. After its conquest by the Christian Normans, the island developed its own distinct culture with the fusion of Latin and Byzantine influences. Palermo remained a leading artistic and commercial center of the Mediterranean well into the Middle Ages.
Map of the main Byzantine-Muslim naval operations and battles in the Mediterranean, 7th to 11th centuries
The Fatimids maintained trade relations with the Italian city-states like Amalfi and Genoa before the Crusades, according to the Cairo Geniza documents. A document dated 996 mentions Amalfian merchants living in Cairo. Another letter states that the Genoese had traded with Alexandria. The caliph al-Mustansir had allowed Amalfian merchants to reside in Jerusalem about 1060 in place of the Latin hospice.
Europe was reviving, however, as more organized and centralized states began to form in the later Middle Ages after the Renaissance of the 12th century. Motivated by religion and dreams of conquest, the kings of Europe launched a number of Crusades to try to roll back Muslim power and retake the holy land. The Crusades were unsuccessful in this goal, but they were far more effective in weakening the already tottering Byzantine Empire that began to lose increasing amounts of territory to the Seljuk Turks and later to the Ottoman Turks. They also rearranged the balance of power in the Muslim world as Egypt once again emerged as a major power in the eastern Mediterranean.
The Crusades led to the flourishing of trade between Europe and the outremer region. Genoa, Venice, and Pisa created colonies in regions controlled by the Crusaders and came to control the trade with the Orient. These colonies also allowed them to trade with the Eastern world. Though the fall of the Crusader states and attempts at the banning trade relations with Muslim states by the Popes temporarily disrupted the trade with the Orient, it however continued.
Slavery
Slavery was a strategic and very important part of all Mediterranean societies during the Middle Ages. The threat of becoming a slave was a constant fear for peasants, fishermen, and merchants. Those with money or who had financial backing only feared the lack of support, should they be threatened with abduction for ransom.
There were several things that could happen to people in the Mediterranean region of the Middle Ages:
When Corsairs, pirate, Barbary corsairs, French corsairs, or commerce raiders plied their trade, a peasant, fisherman, or coastal villager, who had no financial backing, could be abducted or sold to slave traders, or adversaries, who made large profits on an international market;
If the captive was wealthy or had influential supporters, the captive could be ransomed. This would be the most advantageous plan since the money exchange was immediate and direct, not long and drawn out as in the slave market business;
The captive could be used immediately by the corsair for labor on the ship rather than traded. In battles during this era, prisoners of war were often captured and used as slaves.
Emperors would take large numbers of prisoners, parade them through the capital, hold feasts in honor of their capture, and parade diplomats in front of them as a display of victory.