Several hundred veterans of the Japanese Imperial Army took part in the re-creation of the Battle of Saipan, which was filmed on Okinawa. In addition, about 500 U.S. Marines from Camp Hansen on the island were used in this film.
On July 8, 1944, Pfc. Guy Gabaldon single-handedly brought in 800 Japanese prisoners. He is credited with a total of 1,500 from June to August, 1944 from Saipan and Tinian islands.
Guy Gabaldon, who was the technical advisor for the film, was so impressed with Jeffrey Hunter portraying him that he named one of his sons after him.
Guy Gabaldon - unlike Jeffrey Hunter, the tall Anglo actor who played him - was Chicano and only 5'4", 130 pounds. He enlisted in the Marines after Pearl Harbor at age 17.
In the film, Guy Gabaldon's adoptive Japanese-American family the Unes are taken from their home in Los Angeles and sent to an internment camp farther inland for the duration of the war. Actor George Takei, who played George Une, was five years old at the beginning of World War II, and he and his family were sent to an internment camp in Arkansas for the duration of the war because they were of Japanese descent.