Filming began on May 3, 2021, in Puerto Rico. The film was announced that same day as the first part in a pair of films starring Jesse Metcalfe, Bruce Willis, Chad Michael Murray, and Kelly Greyson.
The second film, titled Fortress: Sniper's Eye, was shot simultaneously with the first. Production concluded on November 3, 2021. On May 15, 2021, director James Cullen Bressack said filming on the first film had wrapped.
One of the uniformed military guards is wearing an American Flag patch backwards on their left arm. The field of blue is supposed to be toward the front.