Rob Riggle plays then-LTC Max Bowers, former battalion commander of the 5th Special Forces Group. Riggle, a Marine, actually served directly under the real Bowers during the same time period the movie is based on. According to Riggle, Bowers "loved" his representation in the film.
Gen. Abdul Rashid Dostum was quoted as saying, "I asked for a few Americans, they brought with them the courage of a whole Army", according to Robert Young Pelton in his March 2002 "National Geographic Adventure" article "The Legend of Heavy D and the Boys". Pelton was the only journalist with the Green Beret and CIA team whose story is featured in "Horse Soldiers"
Chris Hemsworth and Elsa Pataky play a couple in the movie. They are married, with kids, in real life.
"Dostum", the last name of the Uzbek general, means "my best friend" in Uzbek and many other Turkic and Indo-European languages.
Michael Peña and Michael Shannon both appeared in World Trade Center (2008), based on the events of 9/11, with Shannon playing a former Marine who turns up at the site to help with the rescue efforts.
Although much of the filming took place near White Sands Missile Range, the scenes involving military encampments were not part of an actual US army installation. The structures were leased from AKS Military, a private company. AKS also provided the military structures for Transformers (2007).
The film is based on Doug Stanton's non-fiction book "Horse Soldiers", which tells the story of CIA paramilitary officers and U.S. Special Forces personnel in addition to USAF Combat Controllers, sent to Afghanistan immediately after the 9/11 attacks. Among the events covered in the book but not in the film is the Qala-i-Jangi prison uprising, one of the bloodiest battles in the early period of the War in Afghanistan.
This is the second time William Fichtner has played a member of Delta Force. He played a composite character, SFC Jeff Sanderson, in Ridley Scott's Black Hawk Down (2001) and plays COL John Mulholland here. Mulholland himself was a staff officer in Delta Force at the time of the 1993 battle in Mogadishu that inspired Mark Bowden's book and the movie.
Navid Negahban, who plays Gen. Dostum, and Numan Acar who plays Mullah Razzanm have both appeared as villains in different seasons of Homeland (2011) and will star together in Aladdin (2019).
The song the Special Forces soldiers sing while in the Chinook helicopter with the lyrics, "... Silver wings upon their chests..." is called 'The Ballad of the Green Beret', by Sgt Barry Sadler. It was popularized during the Vietnam War.
Second collaboration on real-life events among Thad Luckinbill, Kenneth Miller and Geoff Stults, the first being Only the Brave (2017), about the Granite Mountain Hotshots who died in a forest fire.
Many of the US Army Special Forces soldiers seen in the film are seen wearing black fleece jackets. In the book "Horse Soldiers" (renamed "12 Strong" upon the film's release) by Doug Stanton, upon which the film was based, the black fleece jackets were, for some reason, a very popular item amongst the Special Forces personnel as they prepared to go to Afghanistan, so much so that when their original sources ran out of stock, the Special Forces men promptly bought them direct from the manufacturer, North Face.
The B-52s making the bombing run are from Barksdale AFB, Louisiana. This is indicated by the "LA" tail designation on the bomber.
The "paperweight" that the female soldier uses on the unrolled map is a Motorola 9500-series satellite telephone.