Kingdom of Brittany

The Kingdom of Brittany (Breton: Rouantelezh Breizh) was a short-lived vassal-state of the Frankish Empire that emerged during the Norse invasions. Its history begins in 851 with Erispoe's claim to kingship. In 856, Erispoe was murdered and succeeded by his cousin Salomon.
The kingdom fell into a period of turmoil caused by Norse invasions and a succession dispute between Salomon's murderers: Gurvand and Pascweten. Pascweten's brother, Alan, called the Great, was the third and last to be recognized as King of Brittany. After his death, Brittany fell under Norse occupation.
When Alan Twistedbeard, Alan the Great's grandson, reconquered Brittany in 939, Brittany became a sovereign duchy until its union with France in 1532.
In 383, Magnus Maximus was proclaimed emperor by his soldiers in Britain. He promptly invaded Gaul and deposed Emperor Gratian. During the invasion, he instructed some of his soldiers to occupy the western part of the Armorican peninsula and expel soldiers loyal to Gratian. The House of Ingelger confirm this event in their origin story.
At the end of the Antiquity period, additional Celtic Britons, fleeing the Anglo-Saxon settlement of Britain (5th-7th centuries), settled in the same region. At some stage, it was renamed Brittany ("little Britain").
As a result of these settlements, Celtic culture was revived in Gallo-Roman Armorica and independent petty kingdoms arose in this region, namely Cornouaille, Domnonée and Broërec.
From 801 to 837, the adjacent Frankish Empire made several unsuccessful attempts to subdue the Breton tribes. In order to bring Brittany into the Empire's sphere of influence, Louis the Pious appointed Nominoe, a noble Briton, head of the region. Titled missus imperatoris ("Imperial emissary") by the Emperor, he was in charge of the administration of the region on the latter's behalf.
Following the death of Louis the Pious and taking advantage of the Norman invasions destabilizing the Frankish Empire, Nominoe defeated Frankish troops at the Battle of Ballon (845). The peace treaty that followed allowed Nominoe to increase his autonomy from Charles the Bald, a son of Louis the Pious. In 850, the Bretons briefly occupied the Frankish Breton March, but following Nominoe's untimely death they retreated to their historical lands.
Seeking revenge, Charles the Bald invaded Brittany with an army drawn from both the western and eastern parts of the Frankish empire. Erispoe, Nominoe's son and successor, intercepted Charles at the Battle of Jengland (851). At the Treaty of Angers signed the same year, the Pays de Retz entered Erispoe's realm. As the Bretons decisively defeated the Franks, Brittany became effectively independent of the Frankish Empire, making Erispoe the first king of Brittany. In 856, the Kingdom of Brittany and the Frankish Empire allied themselves to counter the Norman invasions. But Erispoe was murdered the same year by his cousin Salomon who took the throne of Brittany and allied himself with the Normans to capture the Frankish city of Le Mans.
Charles the Bald bought peace with the Bretons by giving away the provinces of Cotentin (863) and Maine (867). In 874, Salomon was murdered in a conspiracy involving Pascweten and Gurvand, but a civil war ensued between the latter pair. Both claimants died in 876, but war continued between their respective successors Alan (Pascweten's brother) and Judicael (Gurvand's son).
In a temporary truce, Alan and Judicael allied themselves to counter Norman attacks. In one of those attacks in Questembert in 888, Judicael died and Alan became king of Brittany as Alan I.
Alan died in 907 and was succeeded, after a disputed succession, by Gourmaëlon who did not claim the title of king. Little is known about his reign because Norse raids increased dramatically, destabilizing the region further. It was probably during one of these attacks that Gourmaëlon died in 913.
From 919, Brittany was completely occupied by the Norsemen, monasteries and cities were looted and many Bretons fled to neighbouring countries.
In 935, Alan Twistedbeard (Alan I's grandson), who had fled back to England after a failed insurrection against the Norsemen a few years earlier, disembarked once more on the shores of Brittany in order to reconquer his domain. By 937, he had recovered most of Brittany and the Norsemen retreated to their stronghold of Trans-la-Forêt. In 939, a combined army of Frankish and Breton soldiers attacked the fortress and eliminated the Norse threat in Brittany.
With his domain ruined by decades of occupation and war, Alan Twistedbeard was not in a position to restore the kingship of Brittany and paid tribute as duke of Brittany to king Louis IV of France in 942.