Final answer:
The capital of Lorraine, a region once part of Alsace-Lorraine that fluctuated between French and German control, is Metz. Returned to France after World War I, it was a point of contention leading to significant historical consequences.
Step-by-step explanation:
The capital of the Lorraine region, which was part of the former territory of Alsace-Lorraine, is Metz. Alsace-Lorraine had a tumultuous history, being contested and switching hands between France and Germany over the years.
Following the Franco-Prussian War in 1871, France had to surrender Alsace and Lorraine to the newly formed German Empire, which led to French resentment and desires for revenge. This area was returned to France after World War I with the Treaty of Versailles in 1919, imposing significant territorial losses on Germany. Alsace-Lorraine once again came under German control during World War II but was liberated and restored to France afterwards.