Trench warfare is a form of occupied fighting lines, consisting largely of trenches, in which troops are largely protected from the enemy's small arms fire and are substantially sheltered from artillery. It has become a byword for attrition warfare, for stalemate in conflict, with a slow wearing down of opposing forces.
Trench warfare was the main form of fighting during World War 1 (WW1) when mobility had yet to catch up with the advances made in weapons technology. During the war, the opposing sides would dig large and elaborate trenches, full of tunnels and bunkers. These were then fortified with barbed wires to protect the army from an enemy attack. The area between the two trenches is called "no man's land."
The German Army's invasion of France in 1914 outpaced its supply lines. When the advance was finally halted, both sides dug in. The Western Front became a stalemate. Frontal assaults, nighttime raids, artillery barrages, mortars, and snipers were constant threats from the enemy.
However, the horrendous and unsanitary conditions in the trenches presented an unforeseen enemy. Disease, vermin, mud, and smell of thousands of men living and dying in close quarters, tormented soldiers. Dysentery, typhus, cholera, gangrene, and "trench fever" claimed many lives.
Together with machine guns and poisonous gas, artillery guns played a prominent part in the trench warfare of World War I. Artillery guns were the new and upgraded versions of cannons. But never in the history where there were so many of them used in one single war. Surely artillery guns were to have a huge impact: they accounted for over 60% of the fatalities on western front.
Consider this description of the nightmare of trench warfare: "In the summer clouds of flies feasted on the corpses and then settled on the soldiers' food. Throughout the year large fearless rats roamed the trenches. The reek of death was everywhere . . . Abandoned trenches were often converted into mass graves only to be uncovered when the shelling started again. The soldiers' clothing became infested with lice which were impossible to remove. Constant standing in water often led to 'Trenchfoot' which, if it got out of control, could rot a man's foot away."
Trench warfare can be said to have begun in September 1914 and ended when the Allies made a breakthrough attack in August 1918. Before and after those dates were wars of movement: in between it was a war of entrenchment. The massive armies of 1914 initially fought a war of movement, and any trenches dug were only for temporary cover... The successive movements to outflank (get around the outside of) the enemy trenches came to an end by November 1914. By then there was a continuous line of trenches covering some 400 miles from Switzerland to the North Sea. There was no way round.
from The New Republic, 1915: "There is an illusion that the range and effectiveness of modern arms tend to keep armies far apart. On the contrary, there is more hand-to-hand fighting today than at any time since gunpowder was invented... at this rate the French will not drive out the Germans in months, but on the other hand a frontal attack, and every attack must now be frontal, even if successful would cost several hundred thousand men."
Once trench warfare had literally dug in, all sides involved in the conflict looked for any way possible to bring movement back into their campaigns. One of the more obvious was to develop a weapon that was so appalling that it would destroy not only an enemy frontline but also the will to maintain troops on that frontline. Poison gas might even provoke a mass mutiny along a frontline thus causing it to collapse. In other words, poison gas was the answer for the war's lack of mobility.
Eighteen months later the whole nature of field armies and their tactics changed utterly. In sophisticated trench systems forming a battlefield a few miles wide and 400 miles long, conscript armies sheltered from massive long-range bombardment, wielding new weapons according to new tactical doctrines.
The Germans had closely observed the Russo-Japanese War of 1904-1905 and took note that mortars and grenades, considered militarily obsolete back then, were used to great effect against the entrenched enemy, with grenadiers hurling their grenades into enemy trenches so that supporting infantry could storm the trenches and mop up any survivors...Consequently, when they went to war in 1914, the German's had tens of thousands of hand grenades and even more rifle grenades.
Trenches came about as a result of the German General Erich von Falkenhayn ordered his men to dig in to stop the Allies from advancing any further. Unable to break through this line of German defences the British and French had little option but to defend themselves by digging trenches themselves: otherwise the Germans would have been able to counter attack with ease.