The purpose of an obituary is usually two-fold: first, to provide detailed information regarding the circumstances of the death and burial or memorial events being conducted for the person being remembered; second, to review the important events and activities of the person during his/her life.
Start your obituary with the factual information, some of which you may need to create based on what you know from the story. You will need to provide a date and location of Paul's death as well as explaining the circumstances of his dying.
The review of his life can start with when he was born, where, and the names of his parents. Tell about his accomplishments as a student and about his decision to enlist, which was considered a heroic step at that time. Relate important battles in which he was involved; mention his injuries.
Conclude your review by listing his survivors (family members who are still living) and those who preceeded him in death. You will need to decide if his body is to be returned home for burial or is buried and lost near the battlefield; then you can include information about a funeral or memorial service in his hometown.