I got the sense that the early part of the movie took place well before 1945, so when they first appeared before the battle in 1945, I thought they had already been through battles together. But the battle scenes made it seem it was their first engagement together.
...a medic assigned to 2nd Platoon, B Company, 1st Battalion, 307th Infantry, 77th Infantry Division.
The 77th Infantry Division landed in Hawaii, 31 March 1944, and continued training in amphibious landings and jungle warfare. Elements began to leave Hawaii, 1 July 1944, for the amphibious assault on Guam. Attached to III Amphibious Force, the 77th made an assault landing on Guam, 21 July 1944.
Action was also seen at Leyte.
The division landed on the east coast of Leyte, 23 November 1944, and was attached to XXIV Corps, Sixth Army.
After a short period of training and combat patrolling in the Corps' rear, 23 November – 6 December, it landed at Ipil and fought up the east coast of Ormoc Bay to seize Ormoc, 10 December. Mopping up operations continued through January 1945 to 5 February 1945.
The next combat assignment was Okinawa. In late March (26–29), the division made 15 landings, securing Kerama Retto and Keise Shima for the assault on Okinawa. Riding at sea, 1–15 April 1945, it suffered casualties from enemy suicide attacks, and prepared for the assault landing on Ie Shima. On 16 April 1945, the 77th landed on Ie Shima, captured the airfield, and engaged in a bitter fight for "Government House Hill" and "Bloody Ridge".
Among other decorations, Doss received the Asiatic–Pacific Campaign Medal with 3 battle "stars" and the Arrowhead device indicating involvement in 3 combat assignments and an amphibious assault.