Eugene Sledge was a Marine in the Pacific Theater during WWII. If I recall, he was in his late teens when he enlisted. His nickname was "Sledgehammer."
He wrote a book titled With the Old Breed in part about the horrors of war which he saw with his own eyes.
Sledge also featured as a character in the HBO miniseries The Pacific produced by Steven Spielberg and Tom Hanks.
Indeed Sledge saw terrible brutalities in the war. He felt an ever present fear. He knew firsthand the filth and stench of dead bodies strewn everywhere. The hatred and loathing in one's innermost being for some of the enemy's atrocities.
For instance, Sledge describes a moment when he came across the mutilated bodies of three fellow Marines. One of the dead Marines had had his genitals cut off and shoved into his mouth by Japanese soldiers. It sickened him.
He witnessed many other grotesque events while fighting in the Pacific. He entered the war as a young teenager hoping to have the experience of a lifetime, which he did; but he also came back home mature beyond his years. In many respects, he came back a shattered man, a man with a heavy, pained heart, who had witnessed his friends die before him and much worse. It was as if someone had struck Sledge's heart with a sledgehammer, rending it into pieces.
Although he went on to obtain a PhD in biology, marry a beautiful bride, and raise happy children and grandchildren, these memories never left him. They were forever seared into his mind. Indelible, terrible nightmares.
Later in life, in fact if I recall it was toward the end of his life, and at the encouragement of his wife and other loved ones, he decided to write out about his experiences. Mainly for his friends and family as well as to unburden himself. So he did.
The Marines weren't allowed to keep a diary back then for fear if they were killed in action and their bodies searched, a diary might reveal military secrets to the enemy. However, they were each given a Bible. He had written some notes in his Bible during the war. So he used these notes and his memory to write With the Old Breed.
He didn't expect it to be published let alone to sell so many copies. But it did. Today it's considered a military classic. The book is recommended and sometimes required reading at our military academies and at other universities and institutes.
Sledge ends his book in this way:
Until the millennium arrives and countries cease trying to enslave others, it will be necessary to accept one’s responsibilities and be willing to make sacrifices for one's country - as my comrades did. As the troops used to say, if the country is good enough to live in, it’s good enough to fight for. With privilege goes responsibility.