the number of aircraft on the Fourth Army front to eighteen at Gommecourt. The bombing offensive by the RFC was intended to cut railway links behind the Somme front, south of the Valenciennes–Arras railway and west of the lines around Douai, Busigny and Tergnier. Trains were to be attacked in cuttings, railway bridges were to be bombed and the stations at Cambrai, Busigny, St Quentin and Tergnier were to be raided along with the German ammunition depots at Mons, Namur and the station at Lille were also to be attacked. British aircraft and kite balloons were to be used to observe the intermittent bombardment, which began in mid-June and the preliminary bombardment, which commenced on 24 June. Low cloud and rain obstructed air observation of the bombardment, which soon fell behind schedule and on 25 June, aircraft of the four British Armies on the Western Front attacked the German kite balloons opposite; fifteen were attacked, four were shot down by rockets and one bombed, three of the balloons being in the Fourth Army area. Next day three more balloons were shot down opposite the Fourth Army and during German artillery retaliation to the Anglo-French bombardment, artillery positions were plotted and a Fokker was shot down near Courcelette. Accurate observation was not possible at dawn on 1 July due to patches of mist but by the general effect of the Anglo-French bombardment could be seen. Observers in contact-patrol aircraft could see lines of British infantry crawling into no man's land, ready to attack the German front trench at Each corps and division had a wireless receiving-station for messages from airborne artillery-observers and observers on the ground were stationed at various points, to receive messages and maps dropped from aircraft. As contact observers reported the progress of the infantry attack, artillery-observers sent many messages to the British artillery and reported the effect of counter-battery fire on German guns. Balloon observers used their telephones to report changes in the German counter-barrage and to direct British artillery on fleeting targets, continuing to report during the night by observing German gun-flashes. Air reconnaissance during the day found little movement on the roads and railways behind the German front and the railways at Bapaume were bombed from Flights to Cambrai, Busigny and Etreux later in the day saw no unusual movement, although German aircraft attacked the observation aircraft all the way to the targets and back,