The imperial realm associated with Charlemagne and his successors.
The Carolingian Empire was Latin Christendom's first reconstruction of Rome: Charlemagne's conquests — Lombard Italy (774), Saxony in thirty bitter years, the Avar ring's treasure, the Spanish March — crowned on Christmas Day 800 in Saint Peter's, when Leo III made the Frankish king "emperor governing the Roman Empire".
It legislated a civilisation — capitularies and missi, corrected Bibles and Caroline minuscule, the palace school at Aachen — and then partitioned itself to death: Louis the Pious's sons at the Treaty of Verdun (843) split it into the ancestors of France, Germany, and the contested middle; by 888 the imperial unity was memory, bequeathed as an idea to Ottonian revival.
Charlemagne's forty-six years of campaigns (768–814) roughly doubled Francia: the Lombard kingdom taken with its iron crown (774); Saxony conquered, converted, and repeatedly reconquered (772–804) — the Irminsul felled, the Verden executions (782) and forced baptisms marking the wars' ferocity; Bavaria absorbed (788); the Avar khaganate's ring-fortress plundered into legend (795–796); and the Spanish March carved beyond the Pyrenees after Roncesvalles' famous rearguard disaster (778).
The coronation of 800 crystallised the result: summoned to judge Pope Leo III's cause, Charlemagne left Saint Peter's as emperor — a title Byzantium eventually, grudgingly recognised (812) as "emperor of the Franks". Whether surprise or script, it wedded Frankish power to Roman-Christian universalism: the political theology of medieval Europe in one ceremony.
The empire governed by writing and oath: capitularies (the Admonitio Generalis of 789 a programme for a Christian society), missi dominici — paired count-and-bishop inspectors riding circuit — general oaths of fidelity, reformed silver coinage (the denier standard for centuries), and counts, margraves, and royal vassals knitting three hundred counties to Aachen's palace.
The "Carolingian renaissance" was its soft power: Alcuin of York and an imported intelligentsia correcting texts, schooling clergy, and standardising script — Caroline minuscule, so legible the Renaissance mistook it for Rome's own; scriptoria multiplying the classics (most surviving Latin literature passed through Carolingian pens); Aachen's chapel quoting Ravenna; and the court's self-image — David's new Israel — set in verse and mosaic.
Louis the Pious inherited an empire and an insoluble problem: one imperial title, several throne-worthy sons. The Ordinatio Imperii (817) subordinating brothers to emperor broke on remarriage and rebellion — the Field of Lies (833), penance, and restoration — and after his death the sons fought to the great oath-taking at Strasbourg (842, sworn bilingually in proto-French and proto-German) and the Treaty of Verdun (843): Charles the Bald's west, Louis the German's east, Lothair's imperial middle strip from Frisia to Rome.
The partitions kept subdividing (Prüm 855, Meerssen 870, Ribemont 880) while Vikings burned the rivers, Saracens the Mediterranean, and Magyars (from 899) the east; Charles the Fat's brief reunion collapsed with Paris's siege (885–86) and his deposition (887–88) — "the kingdoms did each make a king from its own guts", a chronicler wrote. The last east-Frankish Carolingian died in 911, the last western claimant in 987: the empire ended, but its idea — translated to Otto I in 962 — and its institutions seeded everything after.
Charlemagne, 768–814, emperor from 800 — the conqueror-legislator of Christian Europe.
Louis the Pious, 814–840 — the reformer whose sons' wars broke the unity.
Lothair I, emperor 840–855 — the middle kingdom's doomed senior line.
Charles the Bald, 843–877 — West Francia's founder-king, emperor at the end.
Louis the German, 843–876 — East Francia's architect.
Charles the Fat, emperor 881–887 — the last reunion and the deposition that ended it.
The empire made correction (correctio) its religion: one Benedictine rule (Benedict of Aniane's synods, 816–17), one liturgy Romanised, one biblical text (Alcuin's), tithes enforced, parishes gridded — the machinery of a uniform Latin Christianity that survived the state which built it. Its theology fought its own battles (predestination, images, the filioque entering the creed at Aachen) with Byzantium watching.
Its society was the manor's: bipartite estates (demesne and dependent holdings) documented in polyptychs like Saint-Germain's, slavery shading into serfdom, and the count-vassal-benefice lattice hardening under invasion into the localised lordship — castles, knights, immunities — that post-Carolingian Europe would call normal. The renaissance's books and the fragmentation's fortresses were the same century's twin bequests.