Question: Why bother to attack in trench warfare?
Because the military leaders of both sides informed by hundreds of years of hard learned experience believed that troops on offense always had the advantage over troops on defense. It was called the cult of offense. The belief in offense over defense was so entrenched in military philosophy even as massive casualties piled it's proponents were characterized with cult like loyalty. The reason for this loyalty to offense was for several centuries history taught that troops on the offense always inflicted more damage than troops on defense. Thus the only reasonable defense was counter attack ( offensive defense). Only technology changed and now due to improvements in fire arms ( wide use of riffles rather than muskets, and most importantly in WWI the wide use of the machine gun), fortified defenses now rather than offense had the advantage.
Experience and study of the military arts blinded military leadership to what they were experiencing. Recent changes in technology and tactics had made offensives in the fashion militaries were used to conducting unacceptable costly. It took several years of costly losses trying to attack entrenched machine guns with infantry to learn the lesson that military truisms which went back before the Napoleonic Wars were no longer valid.
History which generally guides military practices (learn from previous mistakes) is always blind to the latest innovations or tactics. Worse, during WWI historical precedent informed commanders offense was the quickest path to victory. Although already proven wrong in the British Crimean War and American Civil War; conventional wisdom (see Cult of the Offensive) in WWI was offense and massed infantry would overwhelm defensive formations. In the US Civil war and Crimean war conventional wisdom did not account for the Minié ball. In WWI conventional wisdom did not account for the machine gun.
Despite the development of light infantry tactics and the increased effectiveness of firearms during the 19th century, -as was witnessed during the American Civil War and the Franco-German War-, the linear tactics, with massed volley fire, remained the basics of European warfare up to World War I.
In Crimean War(Battle of Balaclava) and the US Civil War(Picket's charge) the Minie ball, which enabled the wide use of rifles over muskets with their vastly improved accuracy and range (4 times the range) turned the Napoleonic tactics of platoon firing into a then unprecedented bloodbath. In WWI the machine gun turned the same tactics of volley fire into mass suicide.
The Bullet which Changed History
Almost as soon as the war(US Civil War) ended, historians began to study the factors that contributed to so much bloodshed – more than 200,000 killed and nearly 500,000 wounded – and concluded that the introduction of the rifle musket was the primary cause of the staggering casualty rates. And not without reason: the rifle musket combined the best features of the smoothbore musket and the Kentucky flintlock rifle. It could be loaded quickly and easily – an experienced soldier could load and fire up to four rounds a minute – while its long, grooved barrel gave it an effective range up to four times that of a smoothbore, with similar improvements in accuracy.
The Minié ball made rifles practical. Now instead of a specialized weapon reserved for sharp shooters and snippers, every man on the battle field could use a highly accurate long ranged riffle without sacrificing loading speed or reliability. The result was casualties skyrocketed as the tactics used for troops carrying smooth bore muskets were still employed for troops now carrying riffles with 4 times the effective range and to my mind even more dramatic improvements in accuracy.
The innovation of a riffle is it has grooves in it's barrel which spin the round as it is discharged. The spin gives the round both improved distance and vastly improved predictability in flight(accuracy). The often unstated ancillary detail is that in order for the round to pick up those grooves and thus receive these benefits, the diameter of the round must be extremely tight with the diameter of the barrel. (modern breach loaded rifles and pistols the rounds are larger than the barrel). This is why bullets are made out of soft metal. The gunpowder forces the overly large round down the narrow barrel and the curves give it the spin. This made riffles exceedingly slow and cumbersome to load, and unsuitable for being the primary infantry weapon until the advent of the Minié ball. The Minie Ball was small when being loaded and it's hollow tail expanded when fired to pick up the grooves in the barrel.
The Minié ball, or Minni ball, is a type of muzzle-loading spin-stabilized rifle bullet named after its co-developer, Claude-Étienne Minié, inventor of the Minié rifle. It came to prominence in the Crimean War and American Civil War. The development of the Minié ball was significant because it was the first projectile which was small enough to be easily put down the barrel of a rifled long gun. Rifling – the addition of spiral grooves inside the gun barrel, which imparted a spin to the bullet – greatly increased the range and accuracy of the gun. Prior to the Minié ball, balls had to be jammed down the rifle barrel, sometimes with a mallet, and after a relatively small number of shots, gunpowder residue built up in the spiral grooves, which then had to be cleaned out.1 Both the American Springfield and the British Enfield rifles – the most common rifles used during the American Civil War – used the Minié ball.
Why did trenches even occur? Because frontal approach of machine gun positions caused so many casualties they couldn't mass enough troops and keep them alive long enough for a proper offensive. Then they figured out that even massed overwhelming infantry emerging from trenches close to the enemy positions still stood no chance against machine guns the stalemate which was WWI began in earnest.
Trench warfare occurred when a revolution in firepower was not matched by similar advances in mobility, resulting in a grueling form of warfare in which the defender held the advantage...
Machine guns at the beginning of WWI weighed whopping 136.5 pounds. Not a problem for defensive troops in pre-fortified positions; a huge incumberance however for advancing troops.
Machine guns inflicted appalling casualties on both war fronts in World War One. Men who went over-the-top in trenches stood little chance when the enemy opened up with their machine guns. Machine guns were one of the main killers in the war and accounted for many thousands of deaths.
Crude machine guns had first been used in the American Civil War (1861 to 1865). However, tactics from this war to 1914 had not changed to fit in with this new weapon. Machine guns could shoot hundreds(600+) of rounds of ammunition a minute and the standard military tactic of World War One was the infantry charge. Casualties were huge. Many soldiers barely got out of their trench before they were cut down.
By 1917, the Germans were reporting that the majority of their small arms ammunition, 90% to be exact, were going into the chambers of their machine guns.
Long story short. Practical military experience historically speaking is a see-saw; for a time the defense will have the advantage and offensive actions bare the primary costs for battles ( see feudalistic middle ages with their great stone castles, or see the machine gun in WWI ); and then everything changes. Some new technological innovation or tactic and the offense has the advantage. Now it's near suicide to be on the defense ( see introduction of cannons and how it changed castles or see the introduction of the Tank and the German Blitzkrieg). The flip side of this is most armies which fight wars, begin their war using the outdated and often suicidal tactics that would have worked well if they used them beginning their last war. ( see WWII, battle of France and the Maginot Line).
Cult of the Offensive
The cult of the offensive refers to a strategic military dilemma, where leaders believe that offensive advantages are so great that a defending force would have no hope of repelling the attack; consequently, all states choose to attack. It is most often used in the context of explaining the causes of World War I and the subsequent heavy losses that occurred year after year, on all sides, during the fighting on the Western Front.
Under the cult of offensive, military leaders believe that the attacker will be victorious (or at least cause more casualties than they receive) regardless of circumstance and so defense as a concept is almost completely discredited. This results in all strategies focusing on attacking, and the only valid defensive strategy being to counter-attack.
During WWII with the advent of new tactics using massed armor this paradigm of offense having the advantage over defense would again exert itself General George Patton would say "Fixed fortifications are a monument to the stupidity of man." Because in WWII this became true again.
We are still going through this pattern today where for a time offense has the advantage and then due to technological advances and new tactics defense has the advantage... In 2006 the Israeli's fought Hezbollah in southern Lebanon. Israel used the tried and true Armor attack supported by air superiority, artillery and infantry. Basically the same tactics Germans used against France and the same tactics Norman Schwarzkopf used against Saddam. Only in 2006 Hezbollah had an answer. Pre fortified tunnels, sophisticated American and Russian anti tank and anti personal missiles. First defeat in Israel's short history of overwhelming militaries victories.. or at least the first time any Israeli Army has left the enemy in the field and retired.
Haaretz Israel’s Second Lebanon War Remains a Resounding Failure
The Israel Defense Forces had fought Hezbollah and Palestinian groups before, but this time it faced an enemy that avoided direct clashes while tailing it at every opportunity and firing Katyusha rockets at the Galilee until the war’s last day. The fact that the IDF couldn’t bring the campaign to a decisive conclusion created great frustration in the government, among the public and in the army itself.
Washington Post 2006 War Called a 'Failure' for Israel
But the panel(Winograd Committee, appointed to examine Israel's conduct of the 2006 war by then Israeli PM Ehud Olmert) did conclude that the war "was a big and serious failure" for Israel, Eliyahu Winograd, the retired judge who led the committee, told reporters.
NyTimes A Disciplined Hezbollah Surprises Israel With Its Training, Tactics and Weapons
Hezbollah, Mr. Goksel says, has clear tactics, trying to draw Israeli ground troops farther into Lebanon. “They can’t take the Israelis in open battle,” he said, “so they want to draw them in to well-prepared battlefields,” like Aita al Shaab, where there has been fierce fighting.
He added: “They know the Israelis depend too much on armor, which is a prime target for them. And they want Israeli supply lines to lengthen, so they’re easier to hit.”
Israeli tanks have been struck by huge roadside bombs planted in expectation that Israeli armor would roll across the border, said one tank lieutenant, who in keeping with military policy would only give his first name, Ohad.
Hezbollah’s Creative Tactical Use of Anti-Tank Weaponry
Among the many aspects to be investigated is the vulnerability of Israel’s powerful armored corps to small, hand-held, wire-guided anti-tank weapons. Indeed, Hezbollah’s innovative use of anti-tank missiles was the cause of most Israeli casualties and has given the small but powerful weapons a new importance in battlefield tactics.