The Treaty of Verdun (Verdun-sur-Meuse, August 843) was a treaty between the three surviving sons of Louis the Pious, the son and successor of Charlemagne, which divided the Carolingian Empire into three kingdoms. It ended the three year long Carolingian Civil War.

When Louis the Pious died in 840, his eldest son, Lothair I, claimed overlordship over his brothers' kingdoms and supported the claim of his nephew Pepin II as king of Aquitaine, a large province in western France. After his brother Louis the German and his half-brother Charles the Bald defeated his forces at the Battle of Fontenay (841) and sealed their alliance with the Oaths of Strasbourg (842), Lothair became willing to negotiate instead of continuing the warfare.

Each of the three brothers was already established in one kingdom: Lothair in Italy, Louis the German in Bavaria, and Charles the Bald in Aquitaine. In the settlement, Lothair (who had been named co-emperor in 817) retained his title as emperor and:

After the death of Lothair in 855, Upper and Lower Burgundy (Arles and Provence) passed to his third son Charles of Provence, and the remaining territory north of the Alps to his second son Lothair II, after whom the hitherto nameless territory was called Lotharingia, which name eventually evolved into the modern Lorraine. Lothair's eldest son, Louis II inherited Italy and his father's claim to the Imperial title.

Verdun (French pronunciation: [vɛʁ.dœ̃]; medieval German: Wirten, official name before 1970 Verdun-sur-Meuse) is a city in the Meuse department in Lorraine in north-eastern France. It is a sub-prefecture of the department.

Verdun is the biggest city in Meuse, although the capital of the department is the slightly smaller city of Bar-le-Duc.

Verdun (Latin: Verodunum, meaning "strong fort") was founded by the Gauls (as its Celtic name shows; "Dunum" is the Latinized version of a Celtic word meaning oppidum). It has been the seat of the bishop of Verdun since the 4th century AD, with interruptions. In the Treaty of Verdun in AD 843, the empire of Charlemagne was divided into three parts.

At around this time Verdun was the centre of a Europe-wide thriving trade selling young boys to be enslaved eunuchs to the Islamic emirates of Iberia. Less controversially, the city has been famous for Dragées or sugared almonds from 1200 onwards; they were distributed at the baptism of French princes.

Verdun was part of the middle kingdom of Lotharingia, and in 1374 it became an Imperial Free City of the Holy Roman Empire. The Bishopric of Verdun formed together with Tull (Toul) and Metz the Three Bishoprics, which were annexed by France in 1552 (recognized in 1648 by the Peace of Westphalia).

World War I (WWI), which was predominantly called the World War or the Great War from its occurrence until 1939 (World War II), and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918. It involved all the world's great powers, which were assembled in two opposing alliances: the Allies (based on the Triple Entente of the United Kingdom, France and Russia) and the Central Powers (originally centred around the Triple Alliance of Germany, Austria-Hungary and Italy; but, as Austria–Hungary had taken the offensive against the agreement, Italy did not enter into the war). These alliances both reorganised (Italy fought for the Allies), and expanded as more nations entered the war. Ultimately more than 70 million military personnel, including 60 million Europeans, were mobilised in one of the largest wars in history. More than 9 million combatants were killed, largely because of enormous increases in lethality of weapons, thanks to new technology, without corresponding improvements in protection or mobility. It was the sixth-deadliest conflict in world history, subsequently paving the way for various political changes such as revolutions in the nations involved.