 Taped lines demarcated German trench lines while officers on horseback carried flags to represent the advancing front of the artillery barrage.Recognizing that the men in leadership positions were likely to be wounded or killed, soldiers learned the jobs of those beside and above them.At the British First Army headquarters, a large plasticine model of the Vimy sector was constructed and used to show commissioned and senior non-commissioned officers the topographical features of the battlefield and details of the German trench system.