text: Galleries were dug to be opened after the attack for communication or cable trenches, the work being done by the 172nd, 176th, 182nd and 185th Tunnelling companies (Lieutenant-Colonel G. C. Williams, Controller of Mines First Army).War in the air
  Although the Royal Flying Corps (RFC) entered the battle with inferior aircraft to the Luftstreitkräfte, this did not deter their commander, General Trenchard, from adopting an offensive posture. Dominance of the air over Arras was essential for reconnaissance and the British carried out many aerial patrols. RFC aircraft carried out artillery spotting, photography of trench systems and bombing. Aerial observation was hazardous work as, for best results, the aircraft had to fly at slow speeds and low altitude over the German defences. It became even more dangerous with the arrival of the Red Baron, Manfred von Richthofen in March 1917. The presence of Jasta 11 led to sharply increased losses of Allied pilots and April 1917, became known as Bloody April. A German infantry officer later wrote,
  The average flying life of a RFC pilot in Arras in April was 18 hours and from 4 to 8 April, the RFC lost 75 aircraft and 105 aircrew. 