The movie was originally about the unsuccessful decade-long manhunt for Osama bin Laden. The screenplay was completely re-written after bin Laden was killed.
The climactic sequence devoted to the raid on Osama's compound runs about 25 minutes, only a few minutes less than the real-life SEALs assault.
Originally conceived as a project about the battle of Tora Bora, Mark Boal completely re-wrote the script after Osama bin Laden was shot and killed. It took him five months and he was not paid for the re-write.
James Gandolfini sent a note to Leon Panetta before the film came out, writing, "I'm very sorry about everything. I apologize. You're like my father, so you'll find something to be angry about, but please let me know." Months later, as the film was in the middle of awards season in early January, screenwriter Mark Boal told Gandolfini, "Leon Panetta would like your phone number because he doesn't know how to get in touch with you." The actor replied "He's the head of the CIA! He can't find me? Come on, really?!"
"Osama bin Laden" is frequently called "UBL" for "Usama bin Laden". There is no standard system for transliterating languages that use non-Latin alphabets, such as Arabic or Pashto, into English. Since the events of September 11, 2001, "Osama" has been the most common rendering of his first name in the American press, but "Usama" has been more common in the intelligence community.