"What It Is Like To Go To War" is Karl Marlantes' extended proposition on how we as a society should approach war and how our warriors should be prepared for what we ask them to do. Marlantes was a young reserve officer in the Marine Corps studying on a Rhodes Scholarship at Oxford University when he entered into active service and was sent to Vietnam. While he was there, Marlantes was an active combat officer commanding fighters in the thick jungle. He witnessed death almost daily and was himself wounded by a grenade, receiving several medals for his actions including the Navy Cross, one of the highest combat awards.

After Vietnam, Marlantes continued his studies at Oxford and went into military intelligence in Washington D.C. He experienced the animosity of many Americans who had opposed the Vietnam war and avoided him or confronted him for his role in the fighting. He struggled with haunting visions and nightmares as well as anger and sought help in the form of therapy. Marlantes writes openly and freely about his experiences and does not shy away from recognizing his own responsibilities.

Based on his own experiences, Marlantes formulates a proposal to better prepare the young soldiers that society expects to go to war. They should be prepared psychologically and emotionally for the real possibility that they will be killing people. They should be expected to treat the enemy with humanity and to use violence ethically. They should be encouraged to recognize that combat can be thrilling and even enjoyable and given the tools to cope with any feelings of shame they have. Marlantes himself admits to enjoying the thrill of combat and reflects on the sadness he now feels in retrospect. The military should also provide veterans with a period of time to "detoxify" after leaving combat and before returning to the more normal civilian world.

Society should recognize its own role in war and in preparing and welcoming back warriors, Marlantes argues. He calls for leaders to adopt a "warrior's dictum" not to use violence except in response to violence and to realize that as leaders with the power to mobilize troops they are warriors themselves. Societies should choose sides carefully and then commit to acting aggressively to end the warfare as quickly as possible. Society should also recognize the conditions that soldiers endure during warfare and find ways to reintegrate them afterwards without causing them to feel ashamed. Finally, Marlantes uses the metaphor of Mars, the Roman god of war, to urge a reconnection of the concepts of war and justice, which were present in the earliest forms of god.