Christian breaks down the early stages of boot camp in "Full Metal Jacket" (1987), with R. Lee Ermey; and "Cherry" (2021), starring Tom Holland. He looks at weapons and physical training in "Forrest Gump" (1994), starring Tom Hanks; "Jarhead" (2005), with Jake Gyllenhaal; "Hacksaw Ridge" (2016), with Andrew Garfield; and "Band of Brothers" (2001). He explains the plausibility of boot-camp scenarios in "Captain America: The First Avenger" (2011), starring Chris Evans; "Private Valentine: Blonde & Dangerous" (2008), with Jessica Simpson; and "Tribes" (1970). Christian also looks at the drill sergeants and drill instructors in "An Officer and a Gentleman" (1982) and "Stripes" (1981), with Bill Murray.

Christian served in the US Army for 33 years as a combat infantryman, with 11 years in the basic training environment. He retired in 2018 as the command sergeant major of Fort Jackson, the Army's main training center for basic combat training. He is now the director of the Warrior PATHH program at the Big Red Barn Retreat, where he helps veterans experiencing post-traumatic stress.