Heeresfeldbahn was a type of train used by the army a long time ago. It was like a big toy train that the soldiers could ride on and use to transport their things like food, water, and weapons.
The tracks where the train went were sometimes made out of metal, and sometimes out of wood. Soldiers would lay the tracks down and then the train could travel on them.
The train had a little engine at the front that helped it move along the tracks. The soldiers could ride inside the train or they could ride on top of it, sort of like a big, bumpy ride at an amusement park.
Heeresfeldbahn was important for the army because it helped them transport all of their things quickly and easily. When the soldiers needed to move to a new location, they could pack everything up on the train and off they would go!