Troops on light rail near Polygon Wood, Belgium

As well as utilising their extensive standard-gauge rail networks for military purposes, the European powers constructed thousands of kilometres of light, narrow-gauge lines to transport troops, ammunition and supplies from main-line railheads to the front. The British light-railway system in the Ypres Salient, Flanders, which was partly constructed and operated by New Zealanders, played a crucial role during the Third Ypres (Passchendaele) campaign of late 1917. These troops from the British 3rd Division, photographed on 25 September 1917, are moving up to take part in the Battle of Polygon Wood.