Editing Battle of Vimy Ridge (section)

===Trench raiding===
{{details|Trench raiding}}
Trench raiding involved making small-scale surprise attacks on enemy positions, often in the middle of the night for reasons of stealth. All belligerents employed trench raiding as a tactic to harass their enemy and gain [[Military intelligence|intelligence]].{{sfn|Cook|1999|p=10}} In the Canadian Corps trench raiding developed into a training and leadership-building mechanism.{{sfn|Cook|1999|p=10}} The size of a raid would normally be anything from a few men to an entire company, or more, depending on the size of the mission.{{sfn|Tucker|1996|p=694}} The four months before the April attack saw the Canadian Corps execute no fewer than 55 separate trench raids.{{sfn|Cook|1999|p=10}} Competition between units even developed with units competing for the honour of the greatest number of prisoners captured or most destruction wrought.{{sfn|Turner|2005|p=41}} The policy of aggressive trench raiding was not without its cost. A large-scale trench raid on 13 February 1917, involving 900 men from the [[4th Canadian Division]], resulted in 150 casualties.{{sfn|Sheldon|2008|p=xi}} An even more ambitious trench raid, using chlorine gas, on 1 March 1917, once again by the 4th Canadian Division, failed and resulted in 637 casualties including two battalion commanders and a number of company commanders killed.{{sfn|Sheldon|2008|p=xi}}{{sfn|Cook|1999|pp=7–24}} This experience did not lessen the extent to which the Canadian Corps employed trench raiding with raids being conducted nightly between 20 March and the opening of the offensive on 9 April, resulting in approximately 1,400 additional Canadian casualties.{{sfn|Sheldon|2008|p=xi}}{{sfn|Turner|2005|pp=41–42}} The Germans operated an active patrolling policy and although not as large and ambitious as those of the Canadian Corps, they also engaged in trench raiding. As an example, a German trench raid launched by 79 men against the 3rd Canadian Division on 15 March 1917 was successful in capturing prisoners and causing damage.{{sfn|Sheldon|2008|p=254}}