At this point I must explain for the benefit of lay readers the difference between a raid and an attack. The purpose of the latter was to drive the enemy from ground he occupied and stay there. Early attacks upon the Western Front were usually directed against trenches, of which successive lines, reaching to a distance or 'depth' of several thousand yards, were often our goal or 'objective.' So that our Infantry could enter hostile trenches it was invariably necessary to destroy the wire in front or make a pathway through it. Many attacks failed because the wire had not been cut. Before the days of Tanks the means employed consisted, broadly speaking, in artillery fire, which it was also hoped would put the enemy's machine-guns out of action and frighten his garrison. Our Infantry advanced immediately this fire had ceased or 'lifted' to the next objective. During the Battle of the Somme it was found that the enemy often left his actual trenches and came forward into shell-holes in No-Man's-Land so as to escape the fire of our artillery. To counter this manoeuvre the 'creeping barrage' was devised. Our shells were fired so as to form a moving curtain of destruction immediately in front of our men in their advance, whilst at the same time the enemy's trenches were bombarded. Attacks on any scale were planned to capture and hold against the enemy some ridge, by losing which he lost observation of our lines, while we, in gaining it, saw more of his and also were enabled to advance our guns. The purpose of a raid was to penetrate a portion of the enemy's front, to kill or capture as many Germans as possible, and then retire. Raids differed materially from attacks in this respect, that no attempt was made in the former to hold the ground won longer than was necessary to satisfy the plan. Raids were usually supported by artillery and took place at night; but daylight raids, though less common or successful, were sometimes made, and 'silent raids,' when no artillery was used, were also tried.