All the proceeds from the film's theatrical run went to nonprofit organizations, including the Elton John AIDS Foundation and other human rights and humanitarian groups.
The priest on the set of film was a real Armenian priest from Armenia that happened to live in Spain. Etchmiadzin, one of the oldest cities in Armenia, has three sister churches and this is where he was ordained. He actually married Oscar and Angela on set, with the true Armenian prayer they would do at any traditional Armenian wedding. Those prayers were true in 1915 and remain the same to this day. He said in the end, "I need to divorce you, because you are technically married in the eyes of God."
The scene between US Ambassador Henry Morgenthau and Turkish Interior Minister Talaat Pasha is taken entirely from Ambassador Morgenthau's memoirs. When Talaat seeks the insurance money for the Armenians he had ordered killed, it is almost verbatim. The memoirs read: "I wish," Talaat now said, "that you would get the American life insurance companies to send us a complete list of their Armenian policy holders. They are practically all dead now and have left no heirs to collect the money. It of course all escheats to the State. The Government is the beneficiary now. Will you do so?" [Henry Morgenthau, Ambassador Morgenthau's Story, New York: Doubleday, 1918, page 339]
According to director and co-writer Terry George he introduced the fictitious character of American journalist Chris Meyers (Christian Bale) to the screenplay of The Promise (2016), because by doing so he could highlight the importance of independent reporting during wartime. He could show what information was being sent across the world around this period of time. The presence of Chris Meyers also allowed for the introduction of real historical figures to the story, such as Henry Morgenthau, who was the American Ambassador to the Ottoman Empire and published memoirs about his experiences. While there was no American journalist named Chris Myers during the Armenian Genocide, his character and reporting is inspired by Armin T. Wegner, Johannes Lepsius and many other historical witnesses.
This feature film was fully financed by billionaire Kirk Kerkorian, who was of Armenian extraction and whose family had lived through these historical events. When he owned MGM in the early 1980s, he couldn't even persuade his own studio chief, Frank Yablans, to greenlight a feature based on Franz Werfel's worldwide bestseller "The Forty Days of Musa Dagh" with global star Clark Gable in the lead, because of Turkey's political pressure on the U.S., who has military bases in Turkey and wanted to keep Turkey as an ally.