Editing Battle of Vimy Ridge (section)

===Preliminary attack===

[[File:Naval gun firing over Vimy Ridge.jpg|thumb|6-inch (150 mm) gun of the Royal Garrison Artillery behind Canadian lines, firing over Vimy Ridge at night|alt=In the black and white photograph, a large artillery gun fires into the night. Personnel are clustered around the artillery, their silhouettes illuminated against the darkened sky. At the muzzle of the artillery, a brilliant white flash bursts forth and contrasts against the black night sky.]]
Foreign intelligence gathering by the Germans, big Allied trench raids and troop concentrations seen west of Arras, made it clear to the Germans that a spring offensive in the area was being prepared.{{sfn|Sheldon|2008|pp=229–237}} In February 1917, a German-born Canadian soldier deserted and helped confirm many of the suspicions held by the Germans, providing them with a great deal of useful information.{{sfn|Sheldon|2008|pp=229–237}} By March 1917, the 6th Army knew that an offensive was imminent and would include operations aimed at capturing Vimy Ridge.{{sfn|Hopkins|1919|pp=157–158}}{{sfn|Sheldon|2008|p=251}} General of Infantry Ernst August Marx von Bachmeister, commanding the German 79th Reserve Division, reported in late March that he believed the Canadian Corps was moving into an [[echelon formation]] and were preparing for a big attack.{{sfn|Godefroy|2007b|p=230}}{{sfn|Sheldon|2008|p=259}} The Germans quickly planned Operation Munich ({{lang|de|Unternehmen München}}), a spoiling attack to capture the northern section of the Zouave Valley, along the northernmost portion of the Canadian front. Munich was not undertaken because the extent of Canadian Corps artillery fire made it impracticable.{{sfn|Sheldon|2008|pp=248–249, 263}}

The preliminary phase of the Canadian Corps artillery bombardment began on 20 March 1917, with a systematic two-week bombardment of German batteries, trenches and strong points.{{sfn|Barris|2007|p=58}} The Canadian Corps gunners paid particular attention to eliminating German barbed wire, a task made easier with the introduction of the No. 106 instantaneous fuse.{{sfn|Cook|2007|p=113}}{{sfn|Barris|2007|p=58}} Only half of the artillery fired at once and the intensity of the barrage was varied to confuse the Germans about Canadian intentions.{{sfn|Barris|2007|p=58}} Phase two lasted the week beginning 2 April 1917 and employed all of the guns supporting the Canadian Corps, massing the equivalent of a heavy gun for every {{cvt|20|yd|m|order=flip}} and a field gun for every {{cvt|10|yd|m|order=flip}}.{{sfn|Nicholson|1962|p=225}} The German soldiers came to refer to the week before the attack as "the week of suffering". In the German account, their trenches and defensive works were almost completely demolished.{{sfn|Nicholson|1962|p=251}}{{sfn|Sheldon|2008|p=273}} The health and morale of the German troops suffered from the stress of remaining at the ready for eleven straight days under extremely heavy artillery bombardment.{{sfn|Sheldon|2008|pp=270–272}} Compounding German difficulties was the inability of ration parties to bring food supplies to the front lines.{{sfn|Barris|2007|p=58}} On 3 April, General von Falkenhausen ordered his reserve divisions to prepare to relieve front line divisions over the course of a long drawn-out defensive battle in a manner similar to the Battle of the Somme and the divisions were kept {{cvt|15|mi|km|order=flip}} from the battlefield to avoid being shelled.{{sfn|Nicholson|1962|p=267}}{{sfn|Godefroy|2007a|p=231}}