From the 850s, Carolingian rule was becoming both fragmented and weaker. Kings from Charles' line continued to vie with brothers and rising notables. At the same time, foreign threats to Europe pressed from the northern, southern, and eastern margins. The first threat came from the Mediterranean area. From the 810s, the Abbasid Caliphate centered at Baghdad started to break apart west of Egypt into smaller emirates led by Abbasid governors. One was the Aghlabid Emirate, centered in Tunisia. Muslims independent of Baghdad controlled Spain. In 825, groups from Spain captured Crete, a Byzantine island. Used from then as a pirate base, Arab Muslims then went on to attack areas all along the southern Mediterranean coast. In 827, the Aghlabids began the conquest of Sicily, completed by the 850s. They proceeded to colonize Sardinia and Corsica, going as far northwest as the Rhone delta in France. Farther east, Aghlabids used Sicily as a base to raid up to Rome in 843, as well as Calabria and Apulia, from which they crossed the Adriatic to harass Dalmatia, and Cyprus. Muslim bases on the Italian mainland continued until 915, when they were ousted by a Byzantine fleet. By 1000, the Muslims had lost Crete, yet the Fatimid Caliphate in Egypt still held Sicily, and the Spanish Ummayads held islands in the western Mediterranean.
The threat from the southeast came in the form of the Magyars, a pagan people originating north of the Crimea. Pushed west by Patzinak Turks in the 890s, they came to Hungary, pushing the Bulgars south. The German King Arnulf asked them to punish the Czech Kingdom of Moravia to the east of Germany and Burgundy in 892. After destroying it in the 900-910s, they turned to raiding in Germany, Italy, as well as Burgundy, France, and Provence. Advancing to Pavia, they wintered in Lombardy in 899, then moving to Carinthia. Next they hit Saxony (906), Bavaria (907), Thuringia (908) and Swabia (909). Two years later, Louis the Child died. The last descendant of Charlemagne from Louis the German, he had been quite weak. German nobles decided to give allegiance to Conrad of Franconia, a non-dominant duke. He was not able to stop Hungarian invasions. From 917-925, they ranged through Basle, Alsace, Burgundy, Saxony, and Provence. During these same years, Conrad's rule had passed to Henry the Fowler, Duke of Saxony. He was the first non-Frankish king of the Germans, and spent the first six years of his rule in fighting of other dukes. Only Franconia was cooperative, with the dukes of Swabia, Lotharingia, and Bavaria resenting his pretensions to untrammeled leadership of eastern Francia.
These civil wars only ended in 924, with new large-scar Magyar raids. In 937, Magyars raided as far west as Reims in France. At first, Henry focused on defending only his home duchy of Saxony. By capturing a Hungarian war leader, he secured a truce for the region. By 933, he felt strong enough to refuse further payments of tribute to the Hungarians. When the Hungarians launched a massive punitive expedition, Henry routed it at Unstrut. In 934 as well, he pushed Danes away from central German lands. When he died in 936, he was hailed as 'lord emperor'. Within twenty years, Magyars receded as a threat to the West. After facing internal revolts similar to those during his father Henry's time, German King Otto I met Magyars in battle at Lechfeld in Bavaria in 955, defeating them so decisively that they never left Hungary again, except to raid lightly in Byzantium. By 1000 the Magyar Duke Stephen Arpad had begun the Christianization process under Papal auspices.
By far more destructive and consequential were the Viking incursions, from the early 800s to the 920s. They affected three major areas: Britain, the Carolingian lands, and Russia. Britain was the first region targeted, starting from the 780s. By 785, monasteries in Lindisfarme (793) and Jarrow were destroyed. Norsemen then began to raid the Shetland Islands, the Orkneys, and the Faroes, after which they moved down between the Western Scottish Islands and Ireland, which became the focus for the next few years. Dublin, Wexford, and Waterford were hit, as was western Scotland. Around this time (820s), the south English King of Wessex was increasing his holdings against the Mercians north of him as well as the Welsh to his west. Wessex was the chief adversary to the Vikings, who refocused their energies on England from the 840s. In 866, the 'great army' of Danish Vikings invaded southeastern England, overrunning East Anglia, Northumbria, and Mercia by 877. They were stopped only by King Alfred the Great (r. 871-899) of Wessex, who defeated them at Edington in 878. By 885, West Saxon power convinced Vikings to make an agreement, whereby only East Anglia, eastern Mercia, and nearby counties would remain in Viking hands, called the Danelaw. Alfred also insisted that Danish Vikings in Britain accept Christianity. By the 920s, Wessex had taken back most of the Danelaw, by which time the Vikings had moved west across the water to Ireland again, establishing the Kingdom of Dublin, which helped them to take York. This area was annexed by the English in 927, when its king died, but was subjected to Scottish-Norse attacks in the 930s. By the 940s, Wessex had established firm control up through York, becoming the Kingdom of Saxon England. By the 950s, only northern Scotland, the Earldom of Orkney, remained as a Viking possession, while the Vikings' places of origin were stabilizing as the Kingdoms of Norway, Sweden, and Denmark.
In Russia, the Swedish Vikings were known as Varangians, invading Slavic lands from the Baltic Sea. By the 860s, the Varangians established three fortified enclaves at Beloozero in the Northeast, Novgorod in the North-Central areas, and Izborsk below the Gulf of Finland. By the 880s, they had extended their raids and migrations south to the Dneiper in the West, with new outposts at Polotsk, Smolensk, and even Kiev north of the Crimea. In the East, they focused on the upper Volga, with new settlements on Rostov and Murom. From there, raids extended at times to Byzantium and Constantinople, with which they also traded. In the next century, Byzantine Emperors assembled a personal protective force called the Varangian Guard. In the tenth century, the Varangians created a unified Russian principality encompassing the region's Slavs and descending to the Crimea. Based on the Rurikovitch dynasty at Kiev, by the middle of the century under Sviatoslav, Varangians had been demographically swallowed by Slavs. The king led expeditions against the Khazars (965), Volga Bulgars (966) and the Lower Danube Bulgar Khanate (967), but was not able to penetrate Byzantine Balkans, and was killed in a Patzinak ambush (972). At this point, both Roman and Orthodox Christianity were making inroads among the Russians. Vladimir I, Prince of Kiev (980-1015), officially accepted the Orthodox rite through an accord with resurgent Byzantium under Basil II (r. 976-1025) whereby he also agreed to marry the Emperor's daughter, establishing lasting cultural ties.
From the 830s-910s, the Norsemen also ravaged Frankish realms. From 814, small summer raids had affected the coast areas such as Nourmoutier at the opening of the Loire. From 840, turning away from Britain for a while, they focused on Europe in earnest, hitting Nourmoutier, Antwerp, and Utrecht. In 841, a Viking fleet entered the mouth of the Seine and sacked Rouen. Two years later they entered the Loire, burned Nantes, moving to plunder the valleys of the Garonne, even threatening Muslim Lisbon. They then wintered on Nourmoutier. As they also established winter bases on Thanet Isle near the Thames, a new phase of occupation-settlement began. From the Loire base they ravaged the Garonne and the Spanish coast. Between 845 and 857, Seville, Bordeaux, Tours, Blois, Orleans, and Poitiers were hit. Beginning it was the sack of Paris with 120 ships. From 859-862 a sustained Viking 'tour' was undertaken. Sailing from Nourmoutier on the Loire, they plundered their why down the French and Iberian coasts, hitting Lisbon on the way. Crossing through Gibraltar, they then raided Morocco, the southern coast of Spain, the Balearic Islands, and Barcelona. The Norsemen then spent the winter on the mouth of the Rhone, near Marseilles. In the next year, they then raided throughout southern France, as far north as Valence. Turning east, they sacked Pisa and Luna in Italy, mistaking the latter for Rome. They then returned to Nourmoutier over the next years, by the same route, ravaging as they went.
In 872, Loire Vikings took Angers, using it as a base for further plundering. This allowed them to hit Ghent (879), Saxony (880), Charlemagne's palace at Aachen (881), Conde (882), and Amiens (883). In 885, a large Viking flotilla proceeded up the Seine, offering to spare Paris only if allowed unhindered passage. The area's duke refused, and a two-year siege commenced. The last strong Frankish king in the East, Emperor Charles the Fat, was able to push them off, offering them a ransom as well as unhampered plundering in Burgundy, his enemy at the time. Viking power began to wane, as German king Arnulf defeated them at Dyle in the Netherlands in 891. They could still dominate weaker western France into the 910s. In 911, Western Frankish king Charles the Simple granted the Viking leader Rollo lands around the mouth of the Seine, soon enlarged to include Normandy. The eventual Normans also accepted Christianity and nominal vassalage to the French King. Defending the region from other Vikings, they would rise through the century from counts to dukes, and become increasingly French. By the 930s, then, the Viking menace ebbed from Europe.
The 840s to the 920s witnessed the last wave of Barbarian influx into Western and Central Europe. Each was more destructive. When the first wave of Goth, Vandal, and Alan incursions passed though Europe's heartland and continued on, they may have destroyed the Roman state, but not necessarily its society, civilization, or culture. The shorter migrations of Franks, Alamanni, and Saxons just west of the Rhine, and then into Gaul, went much farther to wreck Roman civil and political organization, and began to cut off France from the Mediterranean coast in cultural and economic matters. The third wave, consisting of Lombards, Avars, Bulgars, and Slavs, ushered in the Dark Ages for the West and Byzantium, demolishing Antiquity's commercial, and ecological bases, plundering more thoroughly than ever before, having no interest in Roman ideas, and settling the land intensely. No longer continuing migrations, the second and third wave were plundering population transplants.
In the eighth century, Europe witnessed a new invasion in the west, that of Arab and Berber Muslims into Spain. A migration of sorts, it was less destructive. Still, carrying a developing culture and universalist religious message, the Islamic arrival markedly altered Iberia's civilization. Perhaps it was a fourth wave of migrations, but of a decidedly civilized nature. The real fourth wave of Barbarian incursions into Europe occurred with the Viking and Magyar invasions that hastened Carolingian decline. They cut short the flowering of a first medieval European civilization, and were punishing to its culture in a way unlike the previous 200 years. And though the Varangians and Normans would become a part of European society, the majority of Vikings would return to the North after their conversion to Christianity. While some have called the Vikings 'traders not raiders', this seems to exaggerate their commercial tendency directed mostly at the Black Sea and Constantinople region. More probably Vikings themselves would have put it 'mostly raid and a little trade'.
The military stresses on Europe from all sides from 830-950 caused conditions guardedly described as political anarchy. It elicited a further extension of a socio-political process in train already: feudalism. Feudalism did not reach its maturity until the thirteenth century, so only its main lines will be considered here.
In most basic terms, feudalism denotes a socio-political structure based on the granting of land by a superior political power to an inferior one in return for loyalty and services primarily of a military nature. It becomes systemic when the entirety of society is structured around variegated levels of feudal relations. There are two components. The first is a relationship of sworn loyalty to the person of the superior--in this case, the lord. The personal nature of loyalty, as opposed to attachment to an institution, is Germanic in background, quite similar to the comitatus stretching back to the third century. The second component is the tenure on land conditioned on provision of specified services. This has its precedent in late Roman land law.
Since the earliest post-Roman times, counts, generals, and kings had given out lands or revenues in return for some necessary service. Often this was based on a personal loyalty that was sundered at death. A recognizable process of evolution set in from the mid-600s. Provisionally, it consisted of four phases. As later Merovingians weakened, local notables began arrogating fiscal and political prerogatives to themselves. Integral to this process was the emergence of Mayors of the Palace based on local wealth and power. Pepin of Heristal and his descendents typify this. They grew in power in part by cultivating relationships of mutual dependence with other lesser nobility in order to undermine challengers and enfeeble kings. In the process, they alienated lands from the king, and on occasion, from the church that was not in a position to oppose them.
The second phase was under Charles Martel, who in both civil conflict and wars along the southwestern and northeastern frontiers, began to use armored cavalry. This method of warfare was much more expensive than infantry combat, and relatively few warriors could afford to sustain themselves. Charles began to assemble his own retinues. He would personally support a portion of them by providing them shelter, food, and arms in his own residence. By far the larger group was granted lands to sustain them, called benefices, or fiefs (feodum). In both cases, these warriors became vassi dominici-- vassals of the lord based upon an oath of absolute fidelity. This oath made sense when there was no impersonal law common to all in the realm. Such oaths of vassalage most likely bonded lesser nobles to Charles and Pepin III as well. Consultation and consensus with these nobles was integral to the Carolingian rise, until Charlemagne was supreme.
The third phase was attendant upon Carolingian decline and foreign invasions from the 830s. In the political anarchy of civil wars and Viking-Magyar marauding, only armed force through mounted cavalry provided any law or protection. The central army that existed was often ineffective against Vikings. By the time the royal host had assembled, the enemy raid had already passed through, plundering all in its wake. Two dynamics played in to this phase. First, later Carolingians needed armed allies, both to fend off foreigners, as well as to provide militaries to combat their relatives. Thus, kings had to offer something in return for their services: land grants. Second, lesser folk--weaker counts, aspiring warriors, parish priests, and the remaining free peasants--were willing to submit to more powerful men, in hopes of protection or advancement in precarious times. All this contributed to a disbursement of political, legal, and coercive power. Put differently, any authority with a hope of effectiveness had to be local. Thus, varying hierarchies of lord-vassal relations emerged. The feudal process developed soonest and most thoroughly in the regions far from traditional Frankish lands, such as the Western Kingdom, Lorraine, and even Franconia. In these places kings would assign lands to powerful local dukes, who in turn would need to parcel out portions of their fiefs to intermediate warriors in vertical chains through society. At first, land grants were temporary, then given for a lifetime. By the tenth century, in most cases they had become hereditary, based on primogeniture. As it developed, the relationship between lord and vassal took on a more rigid form. If accepted by a lord, the prospective vassal would perform a ceremony whereby he swore fealty to his patron, establishing a personal relationship. Something called homage was associated with this. A term whose difference from fealty is still unclear, homage is thought to involve the acceptance of a fief in return for services, though homage was also performed by members of household retinue receiving no land. In the usual case where a lord was a vassal to a higher figure, the lesser lord's vassals were a boon to the superior leader. As mentioned, services in return for land was key. The nature of them varied from region to region. In every case military service was a component. A vassal was required to serve as much as necessary in defensive efforts for his lord. As regards offensive enterprises, there was usually an upper limit per year, often the forty days corresponding to the spring-summer campaigning season. Often, an added duty was to serve in the garrison of a lord's estate. Beyond this, attendance at the lord's court was necessary, depending upon the position of a vassal in the feudal hierarchy. While it allowed the lord to keep tabs on vassals, and provided him with a judicial corps, it also provided the vassal with an opportunity to have his own views heard, regarding potential campaigns, alliances, or even marriages. Any major project of a lord would require such consultation in order to be practicable. Finally, various ad hoc dues such as hospitality when the lord visited, provision of extraordinary resources at times, and the payment of relief, or a key-money of sorts, when an heir succeeded to a fief, were part of feudal society.
It is not clear that this was the best political arrangement for early-high medieval Europe. It legitimized the enduring personalism of legal relationships, as well as rampant inequality. Also, it was cultivated for the sole purpose of organizing warfare as a means of not just survival, but livelihood and usurpation of kingly authority. Still, it did provide a modicum of local security when far-off kings or senior lords could not. A local vassal was reasonably likely to care for his farms and his villages, as they provided him with sustenance. Thus, a total collapse of society was prevented, and the nuclei of later states were supported in feudal beginnings. Whereas the fourth phase of feudalism was its generalization to the point of no effective kingly power, or his demotion to a first among equals, the emergence of polities on feudal bases would be a fifth stage of feudalism. In the luckiest of cases, the proliferation of medium- and high-level lords allowed more opportunities for elite patronage of culture and arts.