I don't think it is necessary to go into all of the causes of World War I, who is to blame and could it have been prevented. I will leave it up to the historians. If World War II was Hitler's plan to dominate the world, I think one could say that World War I was like a traffic accident. Perhaps one party is more negligent than the other party, but it is still an accident and all parties become victims. Both sides did not fully understand that technology would make war more dreadful than it had ever been. The clue had been the horrendous loss of human life during the American Civil War, but both sides were confident it would be a short and glorious war. There was a terrible loss of life during the Civil War, but now we add the machine gun, chemical warfare, the "aero plane," and tanks which would result in a bloody stalemate called trench warfare. This new type of warfare would mow down young men of both sides like blades of grass.
As with many previous wars, and ones afterward, those who would fight the war, posed for the camera. They seemed too young, even some of the officers. One could see from the pictures that they were proud of their role to serve their country and fatherland. These pictures were probably for their families, wives, and lovers.
The officers were not the only ones who had to get their picture taken. As we see from the picture above and below, privates puffed up with pride in their new uniforms. Here we see the same young man with and without his helmet. He proudly holds his bayoneted rifle (not shown in the first picture) and he is ready for war...or so he may think he is ready.
Along with the individual pictures to be sent to mom and family, all new soldiers had to take a group picture with their new buddies. These buddies would always have a special place in the soldier's heart because they will be the ones to make that journey into battle, to survive, to die, to kill, and to be with them if they survive. They are the true "blood brothers."
Below is yet another photograph but of a group of soldiers finally ready for battle. It is only my guess, but they have not tasted battle yet, their eyes are the clue. They are ready, they seem confident, they seem eager. Look at the soldier in the right front. Does he not seem confident and fearless? The others have various expressions from indifference, to resolve, to perhaps irony.
Look as well to what the soldiers have with them. Each has a gasmask and below them like a friendly dog, lies a machine gun. Poison gas and machine guns would be two distinguishing characteristics of the war.