The trailer note states that Desmond T. Doss was the only soldier to serve in a front-line capacity without carrying a weapon. In WWII, Korea and Vietnam the military classified several Seventh-Day Adventists with the status of 1A-O. This meant that they were willing to serve, but would not carry a weapon in combat. There were also Society of Friends (Quaker) volunteers in WWI.
Producer Hal B. Wallis had previously tried to buy this story from Desmond T. Doss in the 1950s and hoped that Audie Murphy would star, but Doss had no interest in motion pictures and didn't want his story turned into a typical Hollywood movie.
Desmond T. Doss was a member of the US Army's 77th Infantry Division. Known as the "Liberty Division" for its distinctive insignia of a gold Statue of Liberty on a blue background, the 77th fought at Guam, Leyte (Philippines) and Okinawa. One of its units, Company C of the 306th Infantry Regiment, left the US in 1944 with 203 officers and men. By war's end in August 1945, just 13 of the original members were left. The 77th fought alongside the Marines, and a newspaper article during the war described how the division's soldiers fought so well at Guam that they earned the ultimate compliment--the Leathernecks nicknamed their Army counterparts the "77th Marine Division." Famed war correspondent Ernie Pyle was killed by an enemy sniper while covering the 77th on Ie Shima, a small island off the west coast of Okinawa. The 77th was part of the Allied force that occupied Japan after hostilities ceased.
When Dorothy gives Desmond the Bible before leaving for basic training it is bookmarked At 1 Samuel 17. This is the Old Testament account of David and Goliath. Many parallels can be found in these two stories.
Desmond T. Doss was not the first conscientious objector to receive the Medal of Honor. Sgt. Alvin C. York was a conscientious objector also. Gary Cooper portrayed him in Sergeant York (1941). According to Wikipedia, "He [Sergeant York] also disclaimed ever having been a conscientious objector." The important difference being that York did carry a weapon but Doss did not.
Mel Gibson stated that Desmond T. Doss was the first Conscientious Objector in American history to be awarded the Medal of Honor, and he has inspired others to save almost the same number of lives and those inspired have gone on to become recipients of the Medal of Honor.
Vince Vaughn's involvement was his first visit to Australia since Dodgeball: A True Underdog Story (2004). During filming he explored Sydney and its attractions and made headlines when he participated in a public climb of the Sydney Harbour Bridge.
The trivia items below may give away important plot points.
Pfc. Desmond T. Doss was not wounded and evacuated in a daylight assault at Hacksaw Ridge. He was wounded a couple of weeks later in the Okinawa Campaign during a night attack near Shuri. As per his Medal of Honor citation, he was wounded in the legs by a grenade but had to wait five hours before stretcher bearers could reach him, during which time he dressed his own wounds. While being carried back to safety by three stretcher bearers, they were attacked by a Japanese tank. Doss crawled off the stretcher to a more seriously wounded man and insisted the others evacuate that soldier and then return for him. While waiting for the stretcher to return, he was shot by a sniper as he was being carried by another soldier. This caused a compound fracture on his arm, for which he improvised a splint using a rifle stock. He then crawled 300 yards to an Aid Station for treatment.
Mel Gibson stated there were aspects of this event that were true but that he couldn't include in the film because he felt people wouldn't believe they were true: Doss stepped on a grenade to save his buddies and was hit by shrapnel, but as he was being carried away by medics he saw another soldier hurt; since Doss himself was a medic he jumped off his stretcher and treated that soldier and told the medics to take care of other wounded soldiers; he then crawled back to safety while being shot at by enemy snipers.