"Squad D" is the title of a short story by Stephen King. Written in the late '70s, it remains unpublished to date. The story was rejected by Harlan Ellison, who thought it needed work; the anthology "Dangerous Visions III" for which it was intended was never published.
Josh Bortman is the only surviving member of "Squad D". He was in the hospital for hemorrhoids on the day that the other nine members ran afoul of a trap laid by the Viet Cong. Torn apart by guilt, Bortman sends a photo he shot to every family of the victims; it shows the squad, his best and only friends. Three years later, Dale Clewson – father of the late Squad D soldier, Billy – desperately tries to get in touch with Josh, because Josh now can be seen in the photo. But Dale is too late. Josh committed suicide and was hence able to rejoin his friends – in death as well as in the picture. 
The story includes themes and images to which King would return in later works, including survivor's guilt (The Things They Left Behind), the idea of changing pictures (Stationary Bike and Duma Key), and the U.S.'s involvement in Vietnam (Hearts in Atlantis).