It bears the date September 25, 1915, that being the day when the great offensive was launched against the Germans both in Artois and Champagne. On that occasion the map was given only to French officers.
The heavy blue zigzag line shows the front line of the German trenches. The thin blue lines running to the rear show the communication trenches extending back to the second and even the third lines of defense. The French trenches are naturally not shown, but were to the west of the Germans, in some places not over fifteen yards of barbed wire entanglements separating them. At the time of the September attack all these trenches were captured by the French.
The Artois front, which is often called "the sector north of Arras," is one of the most important on the entire line, inasmuch as the army holding the plateau holds also the key to the channel ports. The bloodiest and most desperate battles of the war have occurred there.