[patentatt]

Just happened to be listening to Dan Carlin's hardcore history about WWI. From memory, the Germans would build multiple railway lines to the front to supply a large offensive like this. And then they'd spend weeks stockpiling ammunition and food using those multiple railway lines. At times this conferred a large advantage to the Germans as parts of the Allies side would be supplied by a single road vs. multiple railway lines.

[londons_explore]

When you don't have to deal with boring things like permission to build, consent of landowners, keeping roads open, etc., building a railway is very quick and easy.

[londons_explore]

Building multiple railway lines is also a safety thing - you don't want to leave a whole section of your troops unsupplied just because some train is hit by a shell and wrecked blocking the tracks.