How do soldiers on opposite sides have more in common with their enemy instead of differences other than that they are from different countries?

Although fighting against each other for the glory of their country, the soldiers that fought in World War 1 had many similarities to one another more than they thought. The majority of the soldiers in every country in the war were young men, fresh out of high school or even still in high school, convinced by their parents, teachers, and others that fighting for their country was honorable even if it meant dying. Not knowing the wretched reality of war, these boys volunteered to sign up, smiling, waiting for their uniforms. Many of them had families waiting for them at home to return, but many parents never saw their sons again. Not only are there young men, but men with a family of their own, unable to see their children and wives. 

The living conditions on either side of the war were never comfortable. Everyone is always on high alert and scared of the next attack. Food was scarce throughout the world and hunger killed more than actual fighting. A lot of these boys had dreams of reaching higher rather than being stuck in a trench, clenching a rifle. Instead, their lives were either cut short or their bodies were so damaged that they were unable to do anything with their talent. Unfortunately, the most common similarity between the soldiers on both sides of the war is the loss of adulthood and innocence. There once were young and wild boys, but now there are killers and those afraid to lose their lives.