The modern-day version of Lorraine only covers a small fraction of what Emperor Lothair inherited from his grandfather Charlemagne. The northern half along the North Sea, or Lower-Lorraine, became part of Burgundy, and the southern Upper-Lorraine split up even further. The modern territory of Lorraine covers only about half of this southern region. The Kings of France, the Counts of Luxembourg, and the Counties in the Saar Valley ate away at the ancient Medieval state. By the end of the 18th century, Lorraine had reached its final extent. The King of France felt pity for an exiled Polish King Stanisław Leszczyński and granted him the right to rule in Lorraine. His reign filled the region with palaces and resplendent churches.
Let us go back further in time, to the height of the medieval Duchy of Lorraine. When the Holy Roman Emperor held sway in Lorraine around the 13th century, the region’s politics revolved around the great Bishops in Metz, Toul (and Verdun). The soaring gothic cathedrals of these cities represent their independence from the Emperor in Germany and the King in France. Built-in non-standard French styles, they still fully embrace the fundamental paradigms of the Gothic, a pattern seen in other places with strong French influence, such as in Flanders and Brabant.
Moving to the 15th century, Lorraine was the final stage for the great Burgundy Wars of Charles the Bold and his attempt to reunite Lotharingia. Lorraine was the only piece that King Charles needed to unite Upper and Lower Lorraine. Lorraine was weak and could not count on the French or the Empire to aid them. So Duke Rene of Lorraine hired some Swiss mercenaries, and, following a series of cataclysmic engagements, he saved Lorraine.
With Charles the Bold killed in the Battle of Nancy in 1477, the Burgundian state ended with him. Many historians consider his death the concluding act of the Middle Ages. The “Burgundian Inheritance” would set the stage for the next century with a new kind of war and political conflicts. Though saved from annexation by Burgundy, Lorraine was now permanently tied to the French Kingdom.