Geoffrey II, Duke of Brittany in the context of "Anglo-Norman language"

John (24 December 1166 – 19 October 1216) was King of England from 1199 until his death in 1216. He lost the Duchy of Normandy and most of his other French lands to King Philip II of France, resulting in the collapse of the Angevin Empire and contributing to the subsequent growth in power of the French Capetian dynasty during the 13th century. The baronial revolt at the end of John's reign led to the sealing of Magna Carta, a document considered a foundational milestone in English and later British constitutional history.

John was the youngest son of King Henry II of England and Duchess Eleanor of Aquitaine. He was nicknamed John Lackland (Norman: Jean sans Terre, lit. 'John without land') because, as a younger son, he was not expected to inherit significant lands. He became Henry's favourite child following the failed revolt of 1173–1174 by his brothers Henry the Young King, Richard, and Geoffrey against their father. John was appointed Lord of Ireland in 1177 and given lands in England and on the continent. During the reign of his brother Richard I, he unsuccessfully attempted a rebellion against Richard's royal administrators while the King was participating in the Third Crusade, but he was proclaimed king after Richard died in 1199. He came to an agreement with Philip II of France to recognise John's possession of the continental Angevin lands at the peace treaty of Le Goulet in 1200.

The Treaty of Le Goulet was a treaty signed by Kings John of England and Philip II of France in May 1200. It ended the first succession war following Richard I's death, temporarily settling territorial disputes over Normandy and recognizing John as the rightful heir and King of England. The peace held until Philip's invasion of Normandy in 1202, which led to continental Normandy formal annexation to the crown lands of France.

The treaty was signed at Le Goulet, an island in the middle of the Seine river near Vernon in Normandy. It clarified the feudal hierarchy between the two monarchs, with John acknowledging Philip as his overlord for his French lands. In return, Philip dropped his support for Arthur of Brittany (son of John's late brother Geoffrey) and accepted John's claim to the English throne.

The Duchy of Brittany (Breton: Dugelezh Breizh [dyˈɡɛːlɛs ˈbrɛjs]; French: Duché de Bretagne) was a medieval feudal state that existed between approximately 939 and 1547. Its territory covered the northwestern peninsula of France, bordered by the Bay of Biscay to the west, and the English Channel to the north. It was also less definitively bordered by the river Loire to the south, and Normandy, and other French provinces, to the east. The duchy was established after the expulsion of Viking armies from the region around 939. In the 10th and 11th centuries, it was politically unstable, with the dukes holding only limited power outside their own personal lands. The Duchy of Brittany had mixed relationships with the neighbouring Duchy of Normandy, sometimes allying itself with Normandy, and at other times, such as the Breton–Norman War, entering into open conflict.

Henry II of England invaded Brittany in the mid-12th century and became Count of Nantes in 1158 under a treaty with Duke Conan IV. Henry's son, Geoffrey, became Duke through his marriage to Constance, the hereditary Duchess. The Angevins remained in control until the collapse of their empire in northern France in 1204. The French Crown maintained its influence over the duchy for the rest of the 13th century. Monastic orders supported by the Breton aristocracy spread across the duchy in the 11th and 12th centuries, and in the 13th, the first of the mendicant orders established themselves in Brittany's major towns. A civil war broke out in the 14th century, as rival claimants for the duchy vied for power during the Breton War of Succession, with different factions supported by England and France.

Constance (Breton: Konstanza; c. 1161 – c. 5 September 1201) was Duchess of Brittany from 1166 to her death in 1201 and Countess of Richmond from 1171 to 1201. Constance was the daughter of Duke Conan IV by his wife, Margaret of Huntingdon, a sister of the Scottish kings Malcolm IV and William I. Her first husband was Geoffrey, fourth son of King Henry II of England.

Arthur I (Breton: Arzhur; 29 March 1187 – presumably 1203) was 4th Earl of Richmond and Duke of Brittany between 1196 and 1203. He was the son of Duchess Constance of Brittany, born posthumously to Constance's first husband, Duke Geoffrey II. Through Geoffrey, Arthur was the grandson of King Henry II of England and Duchess Eleanor of Aquitaine, and the nephew of King Richard I of England.

In 1190, Arthur, whose father had died, was arguably designated heir to the throne of England and its French territory, but as he was dying in 1199, Richard I named his youngest brother John heir to the throne, as Arthur was still just a child. Philip II of France thought to make use of a potential succession crisis in England and Brittany and for a while Arthur joined him.