Frankish law always had a problem with inheritance; there’s really no ideal way to manage the inheritance of land. As tribesmen who found themselves ruling a nation, at first they continued their tradition of dividing possessions among a man’s sons. The father had great latitude in who got what; he could design the division afresh in each generation, and he could leave portions of it to the Church. It was obviously fair, unless someone chose to leave his youngest son nothing but a cat (it happens).
However, the 9th and 10th centuries exposed the greatest weakness in this “fair” system. Large estates and kingdoms generally have an advantage; like large schools, they can put together more powerful teams and spend more money. Every time inheritance divided estates, the nation was weakened. At the death of Charlemagne, Frankia was a small empire. It included not only all of modern Germany and France, but also Austria, Switzerland, and most of Italy.
Charlemagne’s successor, Louis the Pious, tried to divide the empire among four sons from two wives, and it was a disaster. In 843, after a civil war,the three survivors signed the first Treaty of Verdun. Lothair was already king of Italy, Louis of Bavaria and Charles of Aquitaine (Atlantic coast). The treaty split up the remaining area in the middle, so that each was now king of either East Frankia, Middle Frankia, or West Frankia. Lothair was the Emperor, and his (not his brothers’) sons inherited the kingdoms. Lothair left his mark on the European map: “Lotharingia,” they called one of his territories, and it came into modern French as “Lorraine.” Still in dispute between France and Germany into the 20th century!
Through the next two centuries, this process happened repeatedly. The empire re-divided into kingdoms and duchies of Aquitaine, Frankia (Neustria), Austria, Bavaria, and Italy, with Lorraine and Provence also in the mix. Sometimes the rulers were brothers, and other times they were cousins. On the plus side, the dynasty stayed personally strong, because it was a never-ending selection process. The king who came out on top in each generation was tall, strong, intelligent and healthy, with good military sense. He was generally very able at driving out invaders. However, each one inherited a slightly different territory with shifting loyalties.
During this period, the Carolingians secured the Mediterranean region that the Romans called “Septimania” away from the Muslims. Septimania had been a “disputed territory” for a few centuries and by the time it was finally in the Frankish column for sure, many of its inhabitants were living in caves, afraid to till their burnt fields. They had to rebuild their civilization to some extent. Septimania was always culturally different; it was more Celtic than the north, and it kept more pre-Christian Roman customs. During the Middle Ages, it became known as Provence and was ruled by a Count, with overlordship by the King of France.
Sicily was under chronic attack from the sea by Muslim invaders all through the 9th century. First they captured Palermo and set it up as a Muslim stronghold. Sicily had been a Byzantine/Greek colony with Syracuse as its capital. The Muslims made great progress at one point when a Byzantine ruler turned on his overlords and allied with Muslim Tunisia (Ifriqiya). In 902, the last Byzantine fortress fell. During the 10th century, Sicily became a Muslim-majority, Arabic-speaking island. Malta went with Sicily; an Arabic-based language is still the mother tongue of the Maltese. Both islands began to cultivate sugar and adopt other Middle Eastern habits.
Around this time, it becomes historically proper to call the Muslims of the Mediterranean islands “Saracens,” while the Muslims of Andalusia gradually became known as the “Moors.”
The Holy Roman Emperor’s responsibility included the coast of southern Italy, although parts of it were nominally controlled by Byzantium. Lothair’s son Louis II inherited Italy and the Holy Roman Emperorship, but somehow the division in this generation cut him out of other continental property. Louis had to split his time between fighting off Saracens along the Italian coast and battling his cousins and brothers. While Louis was fighting Saracens, his family redivided Middle Frankia without dealing him in. While Louis was fighting his family to get Provence, the Saracens took more of southern Italy.
The first Saracen foothold was at Bari, located exactly at the heel of the boot. Local dukes often called in Saracen allies against each other, giving the Muslims town after town. By the middle of the 800s, they were all over southern Italy and attacking Rome itself. Louis II finally turned the tide in 871 by retaking the town of Bari from the Muslims. After this, each generation of Carolingians made progress and by 915, one last huge alliance pushed out the last Muslims from the boot of Italy.
In the final tally, the Franks edged out the Saracens by holding Provence and Italy. The Saracens had firm control of Sicily (and Malta), allowing them a base from which to attack (and trade) anywhere at any time.
The Franks eventually had to face that equal inheritance sounded very fair but was a disaster when the inheritance had to do with military rule, not just property. By the mid 900s, it was clear that something had to give.