It’s no coincidence that every movie Kurt Johnstad writes is about warriors of one stripe or another, from the epic “300” and Relativity Media’s upcoming “Act of Valor,” starring active-duty Navy SEALs, to more recent script assignments like “The Gunslinger,” about an ex-Texas Ranger avenging the murder of his brother.

“Save for a few people in my life, every close male relationship that I have, they’re all warriors, whether they’re SEALs, competitive martial artists or professional mountain climbers,” Johnstad says. “They have a certain code. It’s how I’ve lived my life. You show up, work hard and be humble.”

Johnstad grew up on a large working cattle farm in Wisconsin with two sisters. His father was an Air Force fighter pilot and test pilot who later flew for Pan-Am; his mother was an English teacher. After graduating from high school at 16, he spent a year traveling, then enrolled at CalArts in 1986 to study film and completed the program in just three years.

“A friend of mine said, ‘Do you want to make a couple hundred bucks being a dolly grip?,’ ” Johnstad recalls, and he wound crewing on MOWs and musicvideos for the next four years. Then Zack Snyder, a young commercial director he had worked with once or twice, offered him a job as his first assistant director, and the two spent the next 10 years working side by side.

In the meantime, Johnstad had started writing scripts — including one that actually got produced, the low-budget actioner “True Vengeance” (1995). In 2006, Snyder — who scored a hit with his feature film directorial debut “Dawn of the Dead” (2004) — asked Johnstad to help him adapt Frank Miller’s graphic novel “300,” a fictionalized retelling of the Battle of Thermopylae.

More recently, Johnstad has reteamed with Snyder to co-write the Afghanistan war drama “The Last Photograph” and the sequel “300: The Battle of Artemisia,” both for Warner Bros. The WME client also been hired by producers Basil Iwanyk and Jason Netter to adapt Max Allan Collins’ novel “Black Hats,” set to star Harrison Ford as an aging Wyatt Earp.

Josh Appelbaum & Andrew Nemec | Jay Baruchel & Jesse Chabot | Justin Britt-Gibson | Neil Cross | Andrew Haigh | Kurt Johnstad | Lauryn Kahn | Paula Pell | Jon Spaihts | Brian Yorkey