Carolingian Empire

Mayors of the palace

Drafted from McKitterick, Charlemagne: The Formation of a European Identity (2008)formation

The family that took the imperial title in 800 had been running the Frankish kingdoms for four generations without holding a throne.

The office was mayor of the palace, originally a household steward and by the seventh century the effective head of government, with the Merovingian kings reduced to a ceremonial function that Einhard later described with contempt and that was probably less abject than he made it. Charles Martel held it, beat an Arab raiding force near Poitiers in 732 and campaigned against everybody else, and did not take the crown.

His son Pepin did, in 751, and how he did it set the terms for everything after. He sent to the pope to ask who ought to be called king — the man who had the power or the man who had the title — received the answer he had commissioned, deposed the last Merovingian into a monastery, and had himself anointed with holy oil in a ceremony borrowed from the Old Testament that Frankish kingship had not previously used.

What anointing bought

It made the king a sacred person, and it changed what kingship rested on. A Merovingian was king by being of the blood of Merovech. A Carolingian was king because God, through the church, had made him one — which is a claim available to a family with no blood claim at all, and unavailable to anybody who tried to displace them afterwards without the church's help.

It also created a debt. Pepin crossed the Alps twice on the papacy's behalf against the Lombards and gave the pope the territories that became the papal state. The relationship that produced the coronation of 800 — and the later papal argument that an empire conferred could be withdrawn — starts here, with a usurpation that needed a churchman's opinion.

Charlemagne's wars

He reigned forty-six years and campaigned in most of them, which is a fiscal statement as much as a military one.

The Lombard kingdom in northern Italy was taken in 774 and Charlemagne added its crown to his own. Bavaria was absorbed in 788. The Spanish march was pushed across the Pyrenees, in a campaign whose rearguard was destroyed at Roncesvalles in 778 by Basques and became, three centuries later, the Song of Roland.

And the Saxons. Thirty-two years of war east of the Rhine against a people with no state to surrender, fought by annual invasion, forced baptism, mass deportation and, at Verden in 782, the reported execution of four thousand five hundred prisoners in a day. It ended with Saxony Christian and Frankish, and it is the only sense in which this empire propagated a religion at all.

By 800 the Frankish realm ran from the Ebro to the Elbe and from the North Sea to Rome. Nobody had assembled that much of western Europe since the western Roman empire stopped existing, and the question of what to call the man who had done it was about to be answered in a way nobody in Constantinople accepted.

The Saxons and the Avars

Drafted from Wickham, The Penguin History of Europe (2009)expansion

Two campaigns on the eastern side of the empire did more to determine what kind of state it was than the coronation did, and neither is remembered.

Saxony

The Saxon wars ran from 772 to 804. There was no Saxon king to defeat and no capital to take: the country was a set of regional groupings that could submit, disperse and reassemble, and the Frankish method was to invade every year, extract oaths, build fortresses, and come back when the oaths were broken.

The instruments were baptism and deportation. Submission meant accepting Christianity; the capitulary Charlemagne issued for Saxony in the 780s prescribes death for refusing baptism, for cremating the dead, for eating meat in Lent. Tens of thousands of Saxons were moved west and Franks settled east. It took a generation and it worked, in the sense that Saxony was Christian and Frankish afterwards and produced the dynasty that revived the empire a century and a half later.

It is worth being exact about what that means. Latin Christianity was carried into Saxony, and the instrument was an army. Missionaries followed the capitularies rather than preceding them, and the durable ecclesiastical province that resulted — bishoprics, monasteries, tithes — was built on ground cleared by thirty years of annual invasion. Calling that the spread of a religion is accurate. Calling it anything gentler is not.

The Avar ring

The Avars had held the Hungarian plain for two hundred and fifty years and had spent most of that period extracting subsidies from Constantinople, which paid rather than fight them. The proceeds sat in a fortified encampment the Frankish sources call the ring.

In 795 and 796 Frankish armies took it. The Royal Frankish Annals describe fifteen wagons of gold and silver, each drawn by four oxen, going west. Einhard says that the Franks had been poor and became rich, and lists the gifts Charlemagne sent out of it to the pope, to his followers and to churches across the empire.

What a state without taxation does

That is why the treasure matters more here than a heap of loot usually does.

Wickham's argument is that the single largest difference between the Roman world and the early medieval west is the disappearance of the land tax. A Carolingian king had no assessment, no census, no cadastre and no revenue officials. What he had was his own estates — which were vast — plus tolls, gifts, judicial fines, and whatever the annual campaign produced.

An empire funded that way has to keep campaigning, and its capacity is limited by what the king personally owns. It cannot pay a standing army, so it fights with an obligation on landholders. It cannot pay officials, so it rewards them with land, which they then own.

Two and a half centuries of Byzantine subsidy, paid to the Avars to keep them quiet, moved west in fifteen ox-drawn wagons and made the difference between a poor Frankish reign and a rich one. Einhard says plainly that the Franks had been poor and became rich. That is a description of a state whose finances were an event rather than a system, and the arithmetic of it eventually ran out.

Two emperors, and an embassy

Drafted from McKitterick, Charlemagne: The Formation of a European Identity (2008)peak

On Christmas Day 800 the pope crowned Charlemagne emperor in Rome. There had not been an emperor in the west since 476, and there was already one in the east, who regarded the coronation as a usurpation — the more so because the eastern throne was at that moment occupied by a woman, Irene, which the Frankish position held to mean it was vacant.

The empire itself was Frankish expansion given a Roman title: Gaul, most of Germany after thirty years of Saxon wars, northern Italy, and a march across the Pyrenees. It was administered through counts and royal envoys rather than a bureaucracy, and its most durable product was not political but cultural — a programme of manuscript copying and script reform in the monasteries that preserved the bulk of the Latin literature that survives, in a new hand, Carolingian minuscule, that is the ancestor of the lower case in this sentence.

The elephant

The best evidence that this was one connected world rather than several is an animal.

Charlemagne and Harun al-Rashid exchanged embassies, and Harun sent an elephant named Abul-Abbas, which walked from Baghdad to Aachen and lived there for eight years. Both rulers had a reason. Harun's rival was the Umayyad emirate at Cordoba, in Spain, on Charlemagne's southern frontier. Charlemagne's rival was Byzantium, on Harun's northern one. Each was the other's enemy's enemy, and both courts understood the geography well enough to act on it.

An emperor in Aachen and a caliph in Baghdad, neither of whom could reach the other with an army, worked out that they had the same two problems and could do something about it. The elephant is the part everyone remembers; the strategic calculation behind it is the part that says what the ninth century was actually like.

The empire itself was divided among Louis the Pious's sons at Verdun in 843 and had effectively dissolved by 888 — by inheritance practice rather than by defeat.

Counts and capitularies

Drafted from McKitterick, Charlemagne: The Formation of a European Identity (2008)peak

There was no capital until Charlemagne settled at Aachen in his sixties, and Aachen was a palace with hot springs rather than a city. There was no bureaucracy, no salaried civil service, no permanent archive of the kind that Constantinople and Baghdad ran on, and no tax.

What there was: counts, capitularies and inspectors.

A count held a district, dispensed justice, raised the host and took a third of the judicial fines. He was appointed by the king from the aristocracy, and could be moved — which is the whole difference between this and what came after. Bishops and abbots held comparable authority and were appointed the same way.

Capitularies were the king's written instructions, issued in chapters, on everything from the conduct of counts to the management of royal estates to the correct singing of the liturgy. Several hundred survive. Whether they were enforced is the central argument in the field. McKitterick's position is that the number of surviving manuscript copies made out in the provinces, at local expense, by people who had no obligation to make them, is evidence that they were at least taken seriously by the men expected to obey them.

And the missi dominici, the lord's envoys: pairs of inspectors, one lay and one clerical, sent out in circuits to hear complaints against counts, administer the oath of loyalty and report back. It is a serious attempt at supervision by a government with no standing presence anywhere.

What held it together

Oaths and the aristocracy, mostly.

Every free man was required to swear loyalty to the emperor personally, renewed at intervals and administered by the missi. The great families that supplied the counts were interrelated, held land across the whole empire rather than in one region, and had an interest in the empire staying one thing because their property did not fit inside any single part of it.

That last point is the one that changed, and its changing is the end of the empire. As long as a magnate's estates were scattered from the Loire to the Rhine he needed one emperor. Once the empire had been divided three times and the frontier ran through his holdings, he had to choose a king, and after that he was a regional figure whose interests were regional.

And the books

The court gathered Alcuin from Northumbria, Paul the Deacon from Lombardy, Theodulf from Spain, and set the monasteries copying.

It is worth noticing what kind of government does that. A state with no tax, no bureaucracy and no capital, held together by oaths and the self-interest of a few hundred families, issued written instructions about the correct singing of the liturgy and paid to have the classical Latin literature of the ancient world transcribed. The administration that could barely supervise its own counts was extremely good at producing books, and the books are what survived it.

Down to twelve years of age

Drafted from Select Historical Documents of the Middle Ages (1896)peak

In 802, two years after the coronation, Charlemagne issued a long capitulary setting out what his inspectors were to do and what his subjects had sworn. It survives, and it is the clearest statement anywhere of how a government with no salaried officials, no tax and no capital proposed to govern.

It opens with the inspectors. The emperor chose from among his nobles the most prudent and wisest men — archbishops, bishops, venerable abbots and pious laymen — and sent them over the whole kingdom, so that men should live according to law and right. And where anything in the law is otherwise than according to right and justice, they are to inquire into it most diligently and make it known to him, and he, God granting, hopes to better it.

Then a sentence that tells you who the emperor thought the enemy was. Let no one, through his cleverness or astuteness — as many are accustomed to do — dare to oppose the written law, or the sentence passed upon him, or prevail against the churches of God, or the poor, or widows, or minors, or any Christian man.

The oath, and what it was discovered to mean

The second section is the important one, and the reason it is important is that it is a correction.

Everyone in the kingdom who had sworn fealty to Charlemagne as king was now to swear it again to him as emperor, and everyone who had not sworn was to do so — all, down to those under twelve years of age. And it was to be publicly explained to all of them, so that each one should understand it, how many things that oath contains.

Because, the document says, many had hitherto believed it meant only fidelity as regards the emperor's life, not bringing an enemy into the kingdom, and not consenting to or keeping silent about another man's disloyalty. It means more than that. And the list follows:

Firstly, that every one of his own accord should strive, according to his intelligence and strength, wholly to keep himself in the holy service of God according to the precept of God and to his own promise — inasmuch as the emperor can not exhibit the necessary care and discipline to each man singly.

That clause is the Carolingian state's whole theory of itself. The emperor cannot supervise everybody, so everybody is put under oath to supervise himself, and the oath is given a religious content so that breaking it is a sin as well as a crime. A government that cannot reach into a village has made every adult and every twelve-year-old in it a sworn agent of its purposes.

The rest of the list is more ordinary: nobody is to conceal a runaway imperial slave, or plunder churches, widows, orphans or strangers, or dodge the summons to arms, or let a count release a man from military service for a bribe or out of regard for kinship. And then a clause against professional pleaders — nobody is to make a practice of arguing another man's case in court out of cupidity, or to impede a just judgment by cleverness; each man is to plead his own, unless he is infirm or does not know how, in which case the inspectors or the judge shall plead for him.

What the government was worried about

Read as a list of anxieties rather than as a legal code, the capitulary is candid.

Counts are not to conceal thieves, robbers, murderers, adulterers, magicians or witches under any pretext, induced by reward or flattery. Judges are to judge justly, according to the written law and not according to their own judgment. Bishops and abbots are to have bailiffs and judges who are lovers of justice, because harmful or greedy ones produce the greatest evils. Abbots are to live where the monks are, wholly with the monks. Priests and deacons keeping women in their houses lose their position and their inheritance. Judges, counts and envoys are not to extort payment of a fine from a destitute man after the emperor has forgiven it.

And two clauses that are not about control at all. No one throughout the realm may deny hospitality to the rich, to the poor, or to pilgrims: nobody shall refuse shelter and fire and water to anyone travelling in God's service. And anyone who comes to the emperor's presence seeking alms on account of indigence or hunger, Christian or pagan, is not to be constrained to service, or taken possession of, or sold — and whoever transgresses that shall atone for it with his life.

The feud

The longest single clause is about murder, and its argument is worth following because it shows a government trying to legislate its way out of something it could not police.

It begins with theology — how can any man hope to be pleasing to God who has slain His son, and where can one flee God, to whom all secrets are manifest? — and then arrives at the practical instruction. When a murder has happened, the guilty man is to hasten at once to compound with the dead man's relatives. And then the clause that is really the point:

The relatives of the dead man shall by no means dare to carry their enmity further, or refuse to make peace with him who seeks it; they shall pledge their faith and make a lasting peace, and the killer shall pay the wergeld without delay.

Compensation for killing was old and universal. What this adds is compulsion on the victim's side: the injured family is forbidden to decline the money. An empire held together by oaths and a few hundred interrelated families could survive a great many murders and could not survive the feuds that followed them, and so a capitulary issued in the emperor's name orders grieving relatives, under the royal ban, to accept a payment and shake hands.

The arithmetic

Drafted from McKitterick, Charlemagne: The Formation of a European Identity (2008)contraction

Louis the Pious inherited the whole empire in 814 because his two elder brothers had died, which is the only reason it passed intact. He then spent twenty-six years trying to arrange that it would happen again on purpose.

The Ordinatio Imperii of 817 is a document trying to hold two incompatible things. The empire is to remain one and indivisible, because it is Roman and an emperor is singular. And it is to be divided among the sons, because that is what Frankish inheritance does. Louis's solution was one emperor with two subordinate kings, all three brothers, the younger two owing the elder obedience.

Then a fourth son was born to a second wife, the settlement was reopened to provide for him, and the three elder sons rebelled against their father — twice, deposing him once and restoring him, in a sequence involving a public penance, an assembly at a place called the Field of Lies, and papal intervention on both sides.

Verdun

Louis died in 840 and his sons fought for three years. The Treaty of Verdun in 843 divided the empire into three, and the method is the most revealing detail in the whole business: surveyors were sent out to assess the territories so that the three shares would be equal in revenue.

That is not how a Roman empire is divided. It is how an estate is divided between heirs, and it is the same instinct that broke up the Seljuk and Ayyubid realms in the following centuries: a kingdom treated as family property to be shared out rather than as an office that only one man can hold.

West Francia and East Francia became France and Germany. The middle share, Lotharingia, ran from the North Sea to Rome, had the imperial title and the two capitals, no natural frontier on either side, and was fought over until 1945.

Quierzy

In 877 Charles the Bald, about to leave for Italy, issued a capitulary providing that if a count died while he was away, the count's son should hold the office until he returned to decide.

It was a provision for one absence. It was read afterwards as a concession of what was already happening: that offices held at the king's pleasure, transferable, supervised by travelling inspectors, were becoming hereditary family property.

The arithmetic behind it is simple. A state with no tax rewards its servants with land. Land given is land gone. The Carolingians had given away a great deal of the royal estate over three generations, in benefices that were supposed to revert and did not, and by the 870s a king had less to give and less leverage over the men holding what had already been given.

The Vikings

They arrive in the middle of all this and are usually given the credit.

The raids began in the 790s, became annual and then permanent from the 840s, and by the 880s Viking armies were wintering in the Seine and Loire valleys and besieging Paris. The response — local defence by whoever was there, fortified bridges, payments to make them go away — was necessarily local, and it made the regional commander more important than the distant king.

That is real and it is an accelerant rather than a cause. The empire was already being divided by inheritance and its offices were already becoming hereditary before the great raids started. What the Vikings did was make the case for a regional strongman unanswerable.

888

Drafted from McKitterick, Charlemagne: The Formation of a European Identity (2008)end

Charles the Fat had the whole empire back, briefly, from 884 — not by conquest but because every other adult male Carolingian had died. He held it for three years, failed to relieve Paris from a Viking siege and paid the besiegers to go away instead, and was deposed by an assembly of magnates in November 887. He died two months later.

Nobody replaced him. The Annals of Fulda say that the kingdoms which had obeyed him fell apart into pieces and, not waiting for their natural lord, each made a king out of its own guts.

Five or six kingdoms emerged in a year, and only one of the men who took them was a Carolingian in the male line. That is where the empire stops.

Nobody conquered it

That is worth stating flatly, because it is unusual. Empires normally end because somebody ends them, and where no conqueror is named it is usually because no source survives to name one rather than because there was none.

Here it is positively established that there was no external agent. The magnates of each region chose a king from among themselves. The empire had been divided by inheritance until the pieces were the units that mattered, and the offices had become hereditary until the men holding them were the ones who decided.

The machinery that took the empire apart was the machinery that had been running it all along.

What was left standing

The kingdoms. West Francia and East Francia had been created at Verdun forty-five years earlier and they did not go away; the men who held them in 888 are the beginning of the French and German royal successions.

The church. Bishoprics and monasteries had been endowed with land and privileges throughout, and they were the institutions that survived the ninth century intact, with their libraries, their scriptoria and their claim to appoint their own heads that the eleventh century fought about.

And the title. Otto I — a Saxon, from the people Charlemagne had conquered and baptised at spearpoint — was crowned emperor at Rome in 962, seventy-four years after the last Carolingian emperor was deposed, in explicit revival of Charlemagne's empire. The office went on being claimed for another eight centuries by men who had never held a foot of Frankish ground.

What the empire actually left, though, is not political at all.

What it left behind

Drafted from McKitterick, Charlemagne: The Formation of a European Identity (2008)afterlife

The empire lasted eighty-eight years and its political achievements did not survive the ninth century. Almost everything durable about it is textual.

The Carolingian court gathered scholars from Northumbria, Italy, Spain and Ireland, and set the monasteries to copying. The great majority of surviving classical Latin literature reaches us through Carolingian manuscripts: for most Roman authors the oldest copy in existence is ninth-century, made in a Frankish scriptorium, from a late antique exemplar that afterwards perished. Take that programme out of the ninth century and the western classical canon is a fraction of its size — not because the works would have been condemned, but because parchment rots and nobody else was copying.

The letters

They also reformed the script, and the reform is the reason this is legible.

The hands in use across the post-Roman west had drifted apart into regional varieties that had become nearly unreadable to anybody outside the region that wrote them, run together, heavily abbreviated, and inconsistent from one scriptorium to the next. Carolingian minuscule replaced them with something designed to be read by a stranger: clear letterforms distinguished from one another, words separated by spaces, a functioning lower case, capitals used for a reason.

That is a piece of infrastructure rather than an ornament. A text is only as durable as the next person's ability to read it, and an empire that wanted its capitularies obeyed in Aquitaine and its liturgy sung correctly in Bavaria had a practical stake in a hand that travelled.

Then it travelled further than intended. Italian humanists in the fifteenth century found ninth-century manuscripts of classical authors, took the hand they were written in for the hand of the Romans themselves, and cut their type to match it. Every roman typeface since descends from that mistake. The letters in front of you are a Renaissance reproduction of a Frankish reform of a late Roman cursive, adopted because somebody misdated a manuscript.

What it is not

None of that is a conquest, a conversion or a dynasty, and it is worth being clear that the empire's most durable product is one nobody at the time would have listed among its achievements.

Charlemagne's own reputation rested on Saxony, Italy, the Avars and the imperial title. Two of those were undone within a century of his death and a third passed to a Saxon. The scriptoria were a means to an end — correct texts for a correct liturgy, run by a king who thought a botched psalm was a governance problem.

What survived is the means. The empire fell apart because Frankish inheritance custom took it apart and there was no tax revenue to hold it together; the libraries it endowed were the one asset that could not be divided among three brothers, granted away as a benefice, or lost at Verdun. Bishops and abbots kept them, and went on copying after there was no emperor to ask them to.

Eleven hundred years later the political settlement is a subject for specialists, and the classical literature and the alphabet are common property.

The man in the ox-cart

Drafted from Einhard, Life of Charlemagne (1880)aside?What aside means

Nearly every familiar image of Charlemagne comes from one short book written by a courtier who had served him for over twenty years, on the model of Suetonius, in the 820s, after the man had been dead for some time and the family's grip on the empire had started to slip.

Einhard's Life is the reason we think we know what Charlemagne looked like, what he ate, that he swam, that he kept writing tablets under his pillow and practised making letters and could never manage it. It is also a defence brief, and it is at its most transparent in the first two pages, before Charlemagne has appeared at all.

The kings the family displaced

The book opens on the Merovingians. Einhard is explaining why it was legitimate for his employer's grandfather to take a crown that belonged to somebody else, and his method is to make the somebody else ridiculous.

The Merovingian line, he says, had long since been devoid of vital strength and conspicuous only for bearing the empty title of king. Real power lay with the mayor of the palace. There was nothing left for the king to do but be content with his name, his flowing hair and his long beard, sit on his throne and play the ruler, and receive ambassadors and dismiss them in words that had been suggested to him or imposed on him outright. He owned nothing except the title and one country estate with a small house and enough servants to run it.

And then the detail everybody remembers:

When he had to go abroad, he used to ride in a cart, drawn by a yoke of oxen, driven, peasant-fashion, by a ploughman; he rode in this way to the palace and to the general assembly of the people, that met once a year for the welfare of the kingdom, and he returned home in like manner.

It is devastating, and it is probably not quite true. The long hair was the badge of Merovingian royalty and of free status; the ox-cart appears to have been an ancient royal custom rather than a humiliation, which is why the king used it to travel to the annual assembly of his own people. Einhard has taken two pieces of sacral kingship and presented them as the props of a fool.

Then, three sentences later, he records that the last of them was deposed, shaved, and put into a monastery. Cutting the hair off was the deposition. If the hair had been the empty vanity Einhard has just called it, there would have been no need to cut it.

Why it matters

A courtier writing about a dynasty he serves is not a neutral witness, and this one is unusually easy to catch because he tells you what he is doing. He declines to describe the crossing of the Alps on the grounds that his subject is the manner of the emperor's life rather than the incidents of his wars — having already described the trackless ridges, the heaven-aspiring cliffs and the ragged peaks in the act of refusing. He says it would be folly to write about Charlemagne's birth and boyhood because nothing was ever written on the subject and nobody now alive can supply it, which is an honest admission and also a convenient way past the years when the family's claim was weakest.

The Life is where almost everything vivid about this empire comes from, and the vividness was manufactured by somebody with a position to protect. Both of those things are true at once, and the second one does not cancel the first. It does mean that the picture of the last Merovingian kings — long-haired, useless, trundling to the assembly behind a pair of oxen — is a portrait painted by the people who took their kingdom, and the only one anybody has.

The iron Charles

Drafted from Stammerer, Early Lives of Charlemagne (1907)aside?What aside means

In 883 Charles the Fat spent three days at the monastery of St Gall and asked a monk there to write about his great-grandfather. The book that came of it addresses him throughout as a descendant — your great-grandfather Charles, your most glorious father Lewis, your most religious grandfather Lewis called the pious. The emperor it was written for held the whole empire at that moment, for the last time, and was deposed four years later.

Notker is not Einhard. He had not known Charlemagne, he had few documents, and he takes unusual trouble to say where his material comes from: an old monk of his own house, and that monk's father Adalbert, who had followed the queen's brother through the wars against the Avars, the Saxons and the Slavs. The picture Notker gives of the arrangement is of an old soldier anxious to tell and a young monk unwilling to listen — and the stories were repeated often enough that not only the facts but the words stuck. What he produced is a collection of anecdotes, and its historical value is not what it reports but what it shows: seventy years after the man died, with people who had marched behind him still alive to be asked, the legend was already finished.

Pavia

The set piece is the approach to Pavia in 774, and it is not written like prose.

The Lombard king Desiderius is on a tower with an exiled Frankish noble named Otker, watching the army come. The baggage waggons appear: Is Charles in that vast army? Not yet. The gathered forces of all the nations: Surely Charles moves in pride among those forces. Not yet, not yet. The personal attendants: There is Charles. Not yet, not yet. The bishops and abbots and the clerks of the chapel. At that Desiderius wants to hide himself in the earth. And Otker, who had once had thorough knowledge of the preparations of the unconquerable Charles, tells him what to watch for:

When you see an iron harvest bristling in the fields; and the Po and the Ticino pouring against the walls of the city like the waves of the sea, gleaming black with glint of iron, then know that Charles is at hand.

Then the emperor arrives, and the word is repeated twenty times in a paragraph. An iron helmet, iron gauntlets, an iron breastplate, an iron spear, an iron falchion, iron plates on the thighs, iron greaves, an iron shield, a horse iron-coloured and iron-hearted, everyone around him copying him as closely as possible, the fields filled with iron, the sun's rays thrown back from it. A people harder than iron paid universal honour to the hardness of iron. And from the walls, the cry: Oh the iron! Woe for the iron!

Otker looks at all this and says, There is the Charles that you so much desired to see, and falls to the ground half dead.

Nobody stood on a tower and said that. The refrain, the threefold denial, the watchword, the collapse — it is the shape of a song, written out as prose by a man who had heard it sung.

Why it is worth having

Because of when it was made.

The empire the iron army had built lasted eighty-eight years. Notker was writing in its last decade, for the last man to hold all of it, at a court that would shortly pay a Viking army to leave Paris because it could not beat it. The Charlemagne in his pages — supernaturally shrewd, protector of Jerusalem, terrifying at a distance — is not a memory of a government. It is what a government's descendants tell each other when the government is failing.

And the anecdote he puts nearest this one gives the trick away. Recalling the reign of Charlemagne's grandson, Notker says that Germany was made to pay a penny an acre towards ransoming Christian captives in the Holy Land, and that the appeal was made in the name of the dominion anciently held over that land by your great-grandfather Charles. Charlemagne never held the Holy Land. Somebody was already raising money on the claim that he had.

That is the afterlife of this empire beginning while it is still going. Two centuries later the Crusaders believed they were following Charlemagne's road to Jerusalem; in 1165 an emperor had him canonised; by the Renaissance he was the dim centre of a cycle of poems about knights who never existed. The process starts here, in a monastery in Switzerland, in a book written to flatter a man who was about to lose everything his great-grandfather had assembled.