Scott Adkins and Marko Zaror previously appreared together in Undisputed III: Redemption
The knife used by the Butcher near the beginning of the movie is a Cold Steel Espada with a 5.5 inch blade.
Although in real life Marko Zaror is a Taekwondo practitioner, his character of Rastignac is a master of Savate, a French form of kickboxing.
The narrator/Valentine details the French involvement in the area, preceding U.S. "boots on the ground". Valentine is played by Keith David, who famously played King in Oliver Stone's Platoon, about the U.S. war in Vietnam.
Scott Adkins and Vladimir Kulich previously appeared together in The Debt Collector