The British opposite the 1st Army, received indications that a withdrawal was imminent on 20 and 21 February, when intercepted wireless messages were decoded, ordering German wireless stations at Achiet le Petit, Grévillers and the vicinity of Bapaume, to close and prepare to move back. After this period, information from prisoners and the evidence of German demolitions, indicated that a longer retirement was planned but the existence of three German reserve lines behind the front line, made a local German retirement seem more likely than a longer one. On 13 March, a document revealing the plan and the code-name dated 5 March, was found in Loupart Wood. On 24 February Lieutenant-General Hubert Gough defined the boundaries of the three corps making the advance and ordered them to regain contact with the German armies, using strong patrols supported by larger forces moving forward more deliberately behind them. The German front-line was being maintained along the rest of the front and the possibility of a sudden German counter-offensive was not discounted. On 25 February, the 2nd Australian Division advanced on Malt Trench, found it strongly held and was forced to retire with The Fifth Army divisions advanced with patrols until they met German resistance, then prepared deliberate attacks, some of which were forestalled by German withdrawals, which by 26 February, apart from some small detachments, had abandoned the ground west of the . British engineers improvised sleds to move guns and wagons, with pack-mules being used to carry food and ammunition and on 8 March, ammunition lorries were able to move forward in the V Corps area. Behind the old British front line, the thaw badly affected roads, which had been in a very poor condition at the end of 1916, many were closed and others were limited to horse-drawn traffic. Railway transport was even worse affected, with Boulogne harbour blocked, the number of trains and wagons on the northern French railways far short of British requirements, the lines being congested and subject to traffic restrictions. Supply difficulties had also begun to increase on the Third Army and Fourth Army fronts before the German withdrawals.