Lothair I in the context of "Trpimir I of Croatia"

Lorraine is a historical area of Eastern France that today falls within the administrative region of Grand Est. It was the medieval kingdom called Lotharingia (855–959 AD), after Emperor Lothair I or King Lothair II, which extended further north and came to be ruled by the Holy Roman Empire as the Duchy of Lorraine, before the Kingdom of France annexed it in 1766.

From 1982 until January 2016, Lorraine was an administrative region of France. In 2016, under a reorganisation, it became part of the new region Grand Est. As a region in modern France, Lorraine consisted of the four departments Meurthe-et-Moselle, Meuse, Moselle and Vosges (from a historical point of view the Haute-Marne department is also located in the region), containing 2,337 communes. Metz is the regional prefecture. The largest metropolitan area of Lorraine is Nancy, which was the seat of the duchy for centuries.

The Treaty of Verdun (French: Traité de Verdun; German: Vertrag von Verdun), agreed to on 10 August 843, ended the Carolingian civil war and divided the Carolingian Empire between Lothair I, Louis II and Charles II, the surviving sons of the emperor Louis I. The treaty was the culmination of negotiations lasting more than a year. It was the first in a series of partitions contributing to the dissolution of the empire created by Charlemagne and has been seen as foreshadowing the formation of many of the modern countries of western Europe.

The treaty was the first of the four partition treaties of the Carolingian Empire, followed by the Treaties of Prüm (855), Meerssen (870), and Ribemont (880).

Louis the Pious (Latin: Hludowicus Pius; French: Louis le Pieux; German: Ludwig der Fromme; 778 – 20 June 840), also called the Fair and the Debonaire, was King of the Franks and co-emperor with his father, Charlemagne, from 813. He was also King of Aquitaine from 781. As the only surviving son of Charlemagne and Hildegard, he became the sole ruler of the Franks after his father's death in 814, a position that he held until his death except from November 833 to March 834, when he was deposed.

During his reign in Aquitaine, Louis was charged with the defence of the empire's southwestern frontier. He conquered Barcelona from the Emirate of Córdoba in 801 and asserted Frankish authority over Pamplona and the Basques south of the Pyrenees in 812. As emperor, he included his adult sons, Lothair, Pepin and Louis, in the government and sought to establish a suitable division of the realm among them. The first decade of his reign was characterised by several tragedies and embarrassments, notably the brutal treatment of his nephew Bernard of Italy for which Louis atoned in a public act of self-debasement.

Louis II (825 – 12 August 875), sometimes called the Younger, was the king of Italy and emperor of the Carolingian Empire from 844, co-ruling with his father Lothair I until 855, after which he ruled alone.

Louis's usual title was imperator augustus ("august emperor"), but he used imperator Romanorum ("emperor of the Romans") after his conquest of Bari in 871, which led to poor relations with the Eastern Roman Empire. He was called imperator Italiae ("emperor of Italy") in West Francia while the Byzantines called him Basileus Phrangias ("Emperor of Francia").

Lothair II (835 – 8 August 869) was a Carolingian king and ruler of northern parts of Middle Francia, that came to be known as Lotharingia, reigning there from 855 until his death in 869. He also ruled over Burgundy, holding from 855 just the Upper regions, and from 863 also the Lower Burgundy. He was the second son of Emperor Lothair I and Ermengarde of Tours. He was married to Teutberga (died 875), daughter of Boso the Elder.

The Treaty of Prüm, concluded on 19 September 855, was the second of the main partition treaties of the Carolingian Empire. As Emperor Lothair I was approaching death, he divided his realm of Middle Francia among his three sons.

The Treaty of Mersen or Meerssen, concluded on 8 August 870, was a treaty to partition the realm of Lothair II, known as Lotharingia, by his uncles Louis the German of East Francia and Charles the Bald of West Francia, the two surviving sons of Emperor Louis I the Pious. The treaty followed an earlier treaty of Prüm which had split Middle Francia between Lothair I's sons after his death in 855.

The treaty is referred to in some Western European historiographies as the third major partition of Francia, all of which took place from August 843 to August 870, through the treaties of Verdun, Prüm and Mersen. It was followed by the Treaty of Ribemont.

Bernard (797 – 17 April 818) was the King of Italy, from 810 to 817, within the Carolingian Empire. He was an illegitimate son and successor of King Pepin of Italy. He plotted against his uncle, Emperor Louis the Pious, when the latter's Ordinatio Imperii made Bernard a vassal of his cousin Lothair. When his plot was discovered, Louis had him deposed by the end of 817, and then condemned and blinded, a procedure which killed him.