The decision of G.H.Q. on these questions was that the Channel Ports must be adequately defended at all costs, and that if any sector of the line must be left weakly defended, that sector must be in the southern area, which the Fifth Army had now taken over. The depth of the space available for retirement in rear of the lines in this area no doubt had its influence in this decision; and in addition, the fact that, in the event of a considerable withdrawal of our forces under the pressure of the German attack, a natural line of defence in rear of the forward positions seemed to be offered in the line of the Somme, which at Péronne makes a wide sweep southwards, thus forming a natural barrier more or less parallel with the British front in the St Quentin district. Possibly a further factor was the apparent natural strength of the extreme south of the front between Moy and La Fère, where the Oise Canal and marshes formed a wide and difficult obstacle between the Germans and our own troops. In the southern area, moreover, it would in case of need be more easy to make use quickly of such reserves as the French might be able to place at G.H.Q.'s disposal. II. _The Retreat from La Fère_ The Fifth Army was allotted a front of 42 miles, which was held by 17 divisions in line and 3 infantry and 3 cavalry divisions in reserve. The sector was held by four Corps, from left to right the VII (Congreve), the XIX (Watts), the XVIII (Maxse), and the III (Butler). The III Corps, with which alone we are concerned, comprised at the date of battle the 14th, 18th and 58th Divisions on a front of 30,000 yards, a gigantic sector for 27 battalions, not one of which was at war strength. In reserve were the 2nd and 3rd Cavalry Divisions. The sector allotted to the 58th Division, in which it relieved the 30th between the 7th and 9th February 1918, was the extreme right of the British Armies and extended from north of Travécy, where it touched the 18th Division on the left, to south of Barisis, where it linked up with the French on its right. This enormous front of nearly 9½ miles was held by two brigades, the two subsectors finding their natural division in the Oise marshes and the Canal de St Quentin, which at La Fère take a sudden turn westward, thus running at right angles into the British positions. North of the Canal the country is comparatively open and gently undulating, while south of it the lines plunge through the hilly and densely wooded district of the Forêt de St Gobain.