What are three major reasons that made the WWI so costly in terms of lives lost and overall destruction?

1/ A temporary technological imbalance that favoured defensive over offensive weapons

2/ Artillery was used extensively by all sides to breach defences , and break up attacks, artillery accounted for more lives than any other weapon

3/ The advantage in most cases always favoured the defender , ie Fixed positions , the strength of firepower . In the face of modern rifles , machine guns , and artillery the futility of head infantry assaults was very quickly made apparent . This resulted in both sides concentrating on breaking up any attacks launched by the opposing side.

There are both technological and structural reasons for the carnage and destruction of WWI, the technological being the new innovations in death-technology, like tanks, artillery, gases, etc, and the industrialization behind this technology, which allowed for fast shipment of arms and men, and thus aggravated the death and destruction; while the imperial rivalries and the need for patriotic wars to mobilize restless and often rebellious workers to fight and quickly die for their country and their country's interests in becoming the supreme nation in the world order were some of the structural reasons. There are also ideological reasons, probably, which I can't say for sure, but that there were lots of nationalistic fanaticism in that age, among the different European countries, and there were cultural divides and a general worldview shift, Communism was a threat to the world powers and I think eugenicism might have been popular at the time, thus inflaming ethnic tensions... also, there might have been a general void in values, what with God being dead (Nietzsche) and the rise of the industrial society full of pent up, frustrated egos and men ready to murder foreigners... but I don't know about the ideological sphere that much. ANYWAYS, HOPE THIS HELPS!

The German failure to knock out France early forced them to build strong defensive positions to keep their gains and maintain pressure on the French. This resulted in the stalemate of the trenches.

The trenches were so difficult to breach because advances in firepower (especially artillery, but also machine guns and a number of other technologies) made any attack cost too much to be exploited - at best a small breakthrough would be contained by enemy reinforcements and counterattacks.

The lack of any offensive counters to the trenches until late in the war (new methods of artillery bombardment, tanks, new infantry tactics, cooperation with air forces) also prevented those attacks from being decisive.

While WW I was the first truly "mechanized" war, but it wasn't mechanized to the point where machines were substituted for manpower. Thus, they KILLED a lot more men, but failed to protect them. At the same time, WW I was also the first war where the general citizenry were as much a target as the opposing soldiers and sailors.

3 key man-killing aspects of WW I:

1) Trench and static warfare - long extended periods of battle without serious movement, instead killing opposing soldiers over limited objectives and with little movement (e.g., Battle of the Somme, Marne, Ypres, etc.)

2) Unrestricted use of weapons of mass destruction by all participants (poison gas, machine guns, large artillery bombardments, and aerial bombardment, unrestricted submarine warfare) * See note below.

3) First major war to include intentional attacks upon non-combatant citizens - be they passengers aboard ships attacked by submarine or surface raiders, residents of communities suffering from aerial bombardment or shelling by sea or by artillery, or basic capture and destruction by armies.

* Note: International agreements relating to restrictions on weapons of mass destruction (i.e., the Geneva Convention accords) were not officially recognized when WW I took place.

Magazine loaded bolt action rifles,breech loaded rapid firing artillery,and belt fed machine guns meant defenders were able to deliver massive amounts of firepower over a wide area,at long ranges,quickly.This meant attacks were almost always likely fail with heavy casualties.

Both sides built continuous lines of trenches which,because of the very large armies available,were always well manned with reserves available to replace losses.This meant that all attacks had to be frontal assaults acros open ground against defenders sheltered by their trench systems.

Incompetent senior commanders (particularly on the Allied side) who always believed that a mass frontal attack preceded by a lengthy and heavy artillery bombardment (so the defenders knew exactly where the attack was coming) was going to smash through the enemy lines and end the war in 2 weeks - no matter how many times such ofensives failed with massive casualties.

Destruction was limited - almost all the fighting on the Western Front was in a realtively small area of northeastern France and Belgium,there were no mass air raids on enemy cities,and no major street fighting on any front.