why was world war 1 so devastating, physically and psychologically?

Answer 1

Its combatants used poison gas, machine guns. tanks and trenches for the first time all together and killed millions of young men and civilians. It was "a war to end wars" because it was the last one fought by kings, fighting for nothing but territory.
It need not have been fought at all; the United States had no business blundering into it. And when it was over--our Republican Congress refused to join the League of Nations, and helped bring on World War II only 20 years later in many ways.
So the War became a dividing point between the old graceful but doomed monarchies and a more destructive sort of warfare.

Answer 2

I'll chime in with Robert in that the invention of the machine gun was the most devastating killing machine of the war. "No Man's Ground" which was the the ground between the 2 front lines of the opposing forces (what we now call the FEBA - Front End of the Battle Area) was littered with men killed by this weapon.

Even the invention and introduction of the Tank and the combat aircraft failed to have as much effect either physically or psychologically.

Answer 3

It was the first war where so many countries and different cultures participated and Europe was completely devastated since mostly all of its countries suffered great losses. In addition to this the use of chemicals and other horrible war methods for the first time created the impression that the one side was trying to eliminate the other at any cost and this was very cruel since it removed from war all its noble aspects

Answer 4

It destroyed an entire generation of young men since all the young men in Europe were drafted to go. It saw the invention of terrible, never seen before weapons, like mustard gas which destroyed the lungs and planes. Trench warfare, where soldiers lived in the squalor of the ditches they dug, caused depression and disease. Soliders suffered from battle fatigue. Many battles saw the loss of most of the company. Wounded soliders caught between the lines sometimes could not be rescued because of enemy fire but could be heard moaning or calling for help until they died. Since modern antibiotics had not yet been invented, wounded soldiers were more likely to die of infection and disease than they are now.