West Francia in the 9th century
Charles II, also known as Charles the Bald was the King of West Francia (843-77), King of Italy (875–77) and Holy Roman Emperor (875–77, as Charles II). He’s the grandson of Charlemagne. Charles succeeded by the Treaty of Verdun (843) in acquiring the western third of the Carolingian Empire.
Charles the Bald fought against the Vikings, who devastated the country of the north, the valleys of the Seine and Loire. At the Vikings’ successful siege and sack of Paris in 845 and several times thereafter Charles was forced to purchase their retreat at a heavy price. Charles led various expeditions against the invaders and, by the Edict of Pistres of 864, made the army more mobile by providing for a cavalry element, the predecessor of the French chivalry. He also ordered fortified bridges to be put up at all rivers to block the Viking incursions. Two of these bridges at Paris saved the city during its siege of 885–886.
Charles III (Karl III.), also known as Charles the Fat, was the Carolingian Emperor (881-888). Charles was a great-grandson of Charlemagne. He was the second-last emperor of the Carolingian dynasty and the last to rule, briefly, over a re-united Frankish empire.
He is known to have had repeated illnesses and is believed to have suffered from epilepsy. He twice purchased peace with Viking raiders, including the Siege of Paris (885–886). As a result, Charles’ prestige in France was greatly diminished.
Odo, Count of Paris was a real historical figure too, although he didn’t become king on the show (assassinated in Season 4) .
For his skill and bravery in resisting the attacks of Vikings at the Siege of Paris (885-886), Odo was chosen by the western Frankish nobles to be their king following the overthrow of Emperor Charles the Fat. Odo continued to battle against the Vikings and defeated them at Montfaucon, but was soon involved in a struggle with Frankish nobles who supported the claim of Charles the Simple to the throne.
Gisela, the daughter of Emperor Charls is based on the Princess Gisela, the daughter of Charles the Simple, the grandson of Charls II.
In 911 a group of Vikings led by Rollo besieged Paris and Chartres. Charles decided to negotiate with Rollo, resulting in the Treaty of Saint-Clair-sur-Epte which created the Duchy of Normandy. Rollo also agreed to be baptised and to marry Charles’ daughter Gisela.
It seems that The Emperor Charles of Frankia is based on both Charls the Bald and his grandson Charles the Simple. (and also Charles the Fat?)