Why did Germany annex Alsace-Lorraine after the Franco-Prussian War?

Following the defeat of France in the Franco-German War (1870–1871), Germany annexed Alsace-Lorraine primarily due to the region's ancient German associations and its large German-speaking population.1

While Chancellor Otto von Bismarck reportedly harbored doubts regarding the wisdom of such extensive territorial demands, he was ultimately pressured by German military leaders to secure the annexation. Beyond these historical and cultural justifications, the acquisition provided Germany with significant economic advantages, including valuable iron ore deposits and established iron- and steelmaking industries.21

The annexation served as a definitive conclusion to the conflict, marking the end of French hegemony in continental Europe and solidifying the newly unified German Empire. However, this decision had profound long-term consequences, as the loss of the territory became a primary source of anti-German sentiment in France, fueling the mutual animosity that contributed to the outbreak of World War I.31