The film is based on the true story of the Niland brothers of Tonawanda, New York. The Niland brothers were four of seven siblings, and all of them served in the military during World War II. Three of the brothers - Edward, Preston, and Robert - were killed in action within a few days of each other in June 1944. The fourth brother, Frederick, was also killed in action, but not until 1945.
After the war, the United States Department of War issued a directive that no family would have to bury more than one son in the same war. This directive became known as the "Sullivan Directive," after the Sullivan brothers, who were all killed in action in the Battle of the Solomon Islands in November 1942.
The Saving Private Ryan script is not based directly on the story of the Niland brothers. However, it was inspired by the directive, and it tells a fictional story that explores the themes of sacrifice, duty, and heroism.
While Saving Private Ryan is not a documentary, it is a historically accurate film that depicts the events of World War II in a realistic way. The film was praised for its attention to detail, and it won five Academy Awards, including Best Director and Best Cinematography.