In the Ypres Salient all parties dug tunnels under enemy lines to place mines that were detonated later. Underground warfare reached a peak in 1917 with the Battle of Messines. The attack marked the start of Haig’s Flanders Offensive. Nineteen deep mines were detonated below German lines. After heavy fighting, the New Zealanders took Messines, while Irish and British troops took Wijtschate. Underground activity was not limited to the digging of mineshafts. Dugouts or underground shelters offered protection to a growing number of troops in the devastated landscape. The shelters varied in size and were metres under the ground. The smallest dugout accommodated up to 50 men, while the largest had space for 2,000. In 1918 there were more than 370 such underground shelters in this region. We are now going down into a dugout. Be aware that the cosy atmosphere of the replica can be misleading. Imagine it with damp walls, rising groundwater, vermin and a penetrating smell. There was hardly any ventilation. Dressing stations, latrines and cooking facilities were often right next to each other. Water had to be pumped out of the dugout day and night, sometimes with electric pumps but very often by hand. Nevertheless, the men preferred this dark, wet place of refuge to full exposure to shelling on the surface.