While Zamperini and Phil are floating out at sea on the raft, the picture of a woman that Phil looks at is actually the real photo of his sweetheart and later wife, provided by his daughter to Angelina Jolie during filming.
Universal Studios bought the rights to the story of Louis Zamperini in 1957 in the hope of developing it for Tony Curtis. In later years, Nicolas Cage expressed an interest. The project finally got the green light after Laura Hillenbrand's 2010 book about Zamperini became a best-seller.
Gunnar Höckert, the Finnish runner shown winning the gold medal in the 1936 Berlin Olympics was also a casualty of the Second World War. He went to the Winter War as a volunteer and was killed on the Karelian Isthmus just one day before his thirtieth birthday in February 1940.
Despite being a born-again Christian, Louis Zamperini requested that the film not delve too deeply into his religion, as he wanted his experiences with faith and forgiveness to reach the audience on a universal level.
After the war, Louis Zamperini struggled for several years with PTSD and alcoholism. At the urging of his wife (she threatened to leave him), he attended an early Billy Graham crusade, rededicated his life to Christ, and forgave his captors. Inspired by Louie's powerful testimony, Graham helped him get started in a secondary career of public speaking.
The film was shown at the Casina Pio IV, headquarters of the Pontifical Academy of Sciences and Pontifical Academy of Social Sciences, at the Vatican on January 8, 2015. Pope Francis, who was aware of Louis Zamperini's story, did not attend the screening, but did meet the film's director, Angelina Jolie, and Luke Zamperini, the late athlete's son, afterwards.
It was widely thought that Louie Zamperini would be the first man to break the barrier for the first sub 4 minute mile. History stepped in the way however and that barrier was not broken until Roger Bannister did it in 1954.
Not only the title of the film, but its tagline "Survival / Resilience / Redemption" are inspired by the book the film is based on, "Unbroken: A World War II Story of Survival, Resilience, and Redemption" by Laura Hillenbrand.
The trivia items below may give away important plot points.
While running the Olympic torch in Japan (end of film), the real Louis Zamperini runs past the POW camp in Naoetsu, in which he was held the longest, and is liberated from. This is not mentioned in the film while showing the actual clip during the torch relay.
As stated in the closing titles, the real Mutsuhiro Watanabe refused to meet with Louis Zamperini, however he did agree to be interviewed for a TV program on the occasion of Zamperini's 1998 run in Tokyo. During the interview Watanabe was unrepentant for beating prisoners, but acknowledged that he was not following official orders but "personal feelings" toward his enemies.
The Japanese camps did have a standing order to kill all their POWs. When the war seemed lost, they set a date to carry out that order. The unexpected use of atomic bombs on Hiroshima and Nagasaki a few days before that date aborted their "kill all" plan.