Barrage (artillery)
Development: The moving barrage was developed during the Boer War, one of several tactical innovations instituted under command of General Redvers Buller.  It was a response to Boer defensive positions, notably at Tugela Heights and effective long range rifle fire.
Artillery usually fired over open sights at visible targets, until the Second Boer War when indirect fire started to be used.  The largest unit accustomed to firing at a single target was the brigade (i.e. an artillery battalion), normally 18 guns. Trench warfare led to the necessity for indirect firing through the use of observers, more sophisticated artillery fire plans and an increasingly scientific approach to gunnery. Gunners had to use increasingly complicated calculations to lay the guns. Individual guns were aimed so that their fall of shot was co-ordinated with others to form a pattern; in the case of a barrage, the pattern was a line. The term “barrage” was first used in World War I in English in the orders for the Battle of Neuve Chapelle in 1915.
A lifting barrage was a development in which the barrage lifted periodically to a target further back, such as a second line of trenches. This was countered by the defenders infiltrating troops and machine guns into no-man's land or the areas between their own trench lines, so it was found necessary to comb the entire area of the advance with artillery fire.

Creeping barrage: A creeping barrage (also called a moving barrage) was a barrage that lifted in small increments, usually 50 to 100 yards every few minutes, moving forward slowly, keeping pace with the infantry. British practice evolved to fire at two lines simultaneously. Eventually, three patterns of advancing the barrage developed.  In a creeping barrage, the shell-fire moved from one line to the next. In a block barrage two or more lines were fired on simultaneously and then the fire moved as block to the next lines to be engaged. In a rolling barrage, the fire on the line nearest to their own troops moved to the first unengaged line behind then after a set interval the fire on the second line would move in turn to the next one behind that.
By late 1917, the technique of a creeping barrage had been perfected and could be made to move in complex ways, the barrage wheeling or even combing back and forth, to catch the defenders re-emerging after the barrage had passed but it was still governed by a timetable. A creeping barrage that was too slow would risk friendly fire on one's advancing troops; too quickly could mean that the enemy would have too much time to emerge from cover to resume defensive positions and attack the exposed advancing troops. After World War I the British developed the "quick barrage", a standard barrage pattern that could be ordered by radio without advance plotting of the fire plan on a map.

Standing and box barrages: A standing barrage was static, and might be defensive, to inhibit the movement of enemy troops and break up attacks. A creeping barrage could be made to stand on a line for a time before it moved on, perhaps waiting for the infantry to form up behind it, or to catch up, or perhaps it would stand on the line of known enemy defences, to do more damage and sap enemy morale. The fireplan for the Battle of Messines on 7 June 1917 called for most of the British 18-pounder field guns to fire a creeping barrage of shrapnel immediately ahead of the advance, while the other field guns and 4.5-inch (110 mm) howitzers fired a standing barrage some 700 yards (640 m) ahead.
The standing barrage was aligned with known German positions, and lifted to the next target when the advance reached within 400 yards (370 m) of it. As each objective was taken by the infantry, the creeping barrage would pause at 150 to 300 yards (140 to 270 m) ahead of them and become a standing barrage, protecting the newly gained positions from counter-attack while the infantry consolidated. During this time the pace of fire slackened to one round per gun a minute, enabling the guns and the crews a respite before resuming full intensity as the barrage moved on. The heavy and super-heavy artillery fired on German rear areas. Over 700 machine guns participated in the barrage, using indirect fire over the heads of their own troops.
In a box barrage three or four barrages formed a box – or more often three sides of a box – around a position to isolate it. Standing or box barrages were often used for defensive fire tasks, in which the barrage was registered beforehand on a position – agreed with the defending infantry commander – to be called down in the event of an enemy attack on his positions. A box barrage could also be used to prevent the enemy from reinforcing a position to be attacked. In a trench raid of March 1917, the 1st Battalion the Buffs were supported first by a creeping barrage, then by a box barrage once they were in the enemy trenches, to prevent German reinforcement or counter-attack. It was aided with dummy bombardments on other sections of the line to confuse the enemy.

Advantages and drawbacks: It was soon appreciated how important it was for the attacking troops to follow the barrage closely ("leaning on the barrage"), without allowing time for the defenders to recover from the shock of bombardment and emerge from their dug-outs; the French reckoned they should be suffering 10% of their casualties from their own artillery if they were close enough to the barrage. Ideally the attackers should be into the enemy positions before the defenders had time to recover their composure after the terror of an intense bombardment, emerge from shelters and man their firing positions. On the First day of the Somme, and in the later French Nivelle Offensive on the Chemin des Dames, the barrage outpaced the infantry, allowing the defenders to recover and emerge from their dug-outs, with disastrous results for the attackers. By the end of World War I it was realised that the important effect of the barrage was to demoralise and suppress the enemy, rather than physical destruction; a short, intense bombardment immediately followed by infantry assault was more effective than the weeks of grinding bombardment used in 1916.
A creeping barrage could maintain the element of surprise, with the guns opening fire only shortly before the assault troops moved off. It was useful when enemy positions had not been thoroughly reconnoitred, as it did not depend on identifying individual targets in advance. On the other hand, it was wasteful of ammunition and guns, as much of the fire would inevitably fall on ground containing no enemy.
The World War I barrage with programmed lifts had the effect of confining the infantry advance to the artillery schedule, and of requiring the use of linear tactics, restricting infantry manoeuvre. Infiltration tactics later proved more effective than advancing in rigid lines, and the infiltration phase of German stormtrooper attacks could not use a creeping barrage; but the opening phase of the German spring offensive (Operation Michael) was still supported by a massive creeping barrage, containing a heavy mix of gas shells. The importance of the barrage was such that traditional infantry tactics, such as reliance on the infantry's own firepower to support its movement, were sometimes forgotten.
In the featureless Western Desert in World War II, one benefit of the barrage was that it enabled the infantry to conform their line to the barrage, ensuring that their line of advance was correct. By 1943 the barrage was considered to dissipate firepower and to constrain the infantry into advancing in rigid lines.
A barrage could severely churn up the ground, especially in soft going, and impede the progress of the attacking troops.

Use in World War I: It is sometimes claimed that creeping barrage was first used during World War I in the battle of Gorlice in May 1915 (part of the Gorlice–Tarnów offensive) by General Tadeusz Rozwadowski, but in fact infantry assault was simply preceded by a four-hour shelling of the Russian defences. The first day of the battle of the Somme saw another attempt at a large-scale creeping barrage which had been planned in anticipation of the infantry's anticipated ability to advance relatively unhampered across the battlefield due to a heavy, week-long preparatory bombardment. For example, on XV Corps front, the barrage was programmed to lift 50 yards (46 m) every minute. Complications arose however in British protocols to prevent friendly-fire casualties which at the time dictated that shellfire was to be kept over one hundred yards away from their own uncovered infantry.  In many cases no man's land was narrower than the allowable 'safe' distance and as such the barrage did not protect the men as they went 'over the top' and advanced towards the German trenches.
Further, as the British infantry was slowed far beyond the expected pace of advance across no-man's land, all along the Somme front it proved impossible for the infantry to keep up with the pace of the barrage. However, the tactic was further refined as the Battle of the Somme wore on and by September 1916 the creeping barrage became a standard tactic for infantry attacks, and soon spread to the French Army, enabling the French recapture of Fort Vaux at the Battle of Verdun in November 1916. By the later stages of the Battle of the Somme, the British had improved the accuracy of and confidence in their artillery fire and had learned the lessons of keeping infantry close to the barrage: the British Expeditionary Force (BEF) circulated an aerial observer's report commending a "most perfect wall of fire" followed up within 50 yards (46 m) by the infantry of 50th (Northumbrian) Division, enabling them to take a village with little opposition.