Wikipedia
Kanonenbahn
The Kanonenbahn (literally "Cannons Railway") is a former German military strategic railway between Berlin and Metz via Güsten, Wetzlar, Koblenz and Trier. Metz is in Alsace-Lorraine, which was annexed by Germany after the Franco-Prussian War.
Other railways, such as the Glan Valley Railway (Glantalbahn), built mainly for military strategic reasons, were also colloquially known as the Kanonenbahn, but the link between Berlin and Metz is the best known of them.