and machine-gunners free to fire into the right flank of the 25th Division. German counter-attacks continued into the night but communication by SOS rockets, daylight lamps, carrier pigeons and runners, enabled the British artillery accurately to bombard German troops as they assembled. Background Topography Ypres is overlooked by Kemmel Hill in the south-west and from the east by low hills running south-west to north-east, with Wytschaete (Wijtschate) and Hill 60 to the south of Verbrandenmolen, Hooge, Polygon Wood and Passchendaele (Passendale). Wytschaete is from Ypres, at Hollebeke the ridge is distant and recedes to at Polygon Wood. Wytschaete is the highest point, about above the plain; on the Ypres–Menin road at Hooge, the elevation is about and at Passchendaele. The rises are slight, apart from the vicinity of Zonnebeke, which has a gradient of From Hooge and to the east, the slope is near Hollebeke, it is The heights are subtle and resemble a saucer lip around the city. The main ridge has spurs sloping east and the spur at Wytschaete, runs south-east to Messines, with a gentle slope to the east and a to the west. Further south is the muddy valley of the Douve river, Ploegsteert Wood (Plugstreet to the British) and Hill 63. West of Messines Ridge is the parallel Wulverghem (Spanbroekmolen) Spur, with the Oosttaverne Spur, also parallel, further to the east. The general aspect south and east of Ypres is one of low ridges and dips, gradually flattening northwards beyond Passchendaele into a featureless plain. Possession of the higher ground to the south and east of Ypres gives ample scope for ground observation, enfilade fire and converging artillery bombardments. An occupier also has the advantage that the movement of artillery, reinforcements, supplies and stores can be screened from view. The ridge had woods from Wytschaete to Zonnebeke giving good cover, some being of notable size like Polygon Wood and those later named Battle Wood, Shrewsbury Forest and Sanctuary Wood. In 1914, the woods usually had undergrowth but by 1917, artillery bombardments had reduced the woods to tree stumps, shattered tree trunks and barbed wire, tangled on the ground and a mass of shell-holes; the fields in gaps between the woods were wide and devoid of cover. Most roads in this area were unpaved, except for the main ones from Ypres, with occasional villages and houses built along them. In 1914, the lowland west of the