There were enormous numbers of loss of lives. For example 315000 French soldiers died at the war in Verdun only in 10 months. The nonstop death of the soldiers are caused by the people who were controlling people caused the non-stop death of the soldiers. Garry Sheffield once said that those soldiers were "Lions led by Donkeys", which was unarguable. Douglas Haig was the leader of the British at the battle of Somme. His ways of battles were not logical which made many of his troops to deathget killed.
Many immature young soldiers fought in the war, after all there were large numbers of widows and orphans left after this war. There were 8.5 million people killed and 33 millions wounded.
This is a direct factor because it was what that war has made directly to the people.
Hunger and disease were among many indirect factors that were caused by the war.
The food was not enough and it was hard to transport it to the fronts . There were also some diseases caused by the war. Soldiers had extremely hard times in the trenches. It was cold and wet all over. The drains were destroyed because of artillery and most of them were drowned. Soldiers were not able to take medicines. If someone there gets shot or hurt doctors only had to use knives, they didn't have any anesthetics.
The shooting and killing of innocent citizens, the way of treating the women, destroying important places such as the Red Cross were completely sadistic. Those things happened in France and Belgium during the war. For example 3 France innocent people of the same family were cruelly killed because they refused to bake a breadbread to the Germans.
This can be direct because they are being treated like this because of the Germans, it's not caused by the war such