Creator Tony Grounds was inspired by a story he heard while visiting an army base about a young woman who was 'angry as a feral cat' at the start of basic training but became a calm, professional combat medic in Afghanistan.

The pilot was commissioned after BBC drama executive John Yorke asked Tony Grounds if he had any ideas for Lacey Turner, and the pilot took three years to complete after their initial meeting.

After Lacey Turner left the show to return to EastEnders as Stacey Slater, Michelle Keegan was cast as new protagonist Georgie Lane, and she met with real army medics to prepare for the role.

Jacqueline Jossa, another former EastEnders actress, was reportedly in advanced talks to replace Michelle Keegan as the lead had the show been renewed for a fifth series.

Although set in Afghanistan, the first series was filmed over 49 days at the Serra Della Camp in the Bonte Bok mountain range in South Africa, where strong winds sometimes blew over buildings and damaged production equipment, requiring steel hawsers to secure the sets.

Actors underwent roughly 10 months of training for the first series, and for later series attended boot camps in the UK and South Africa, including using real weapons, to prepare for filming in heavy military attire and heat.

For series 3, part of the story was filmed on location in a village near Kathmandu, Nepal that had actually been affected by the April 2015 Nepal earthquake, with the art department enhancing the visible damage to match the plot.

Luke Pasqualino told creator Tony Grounds he intended to leave the show after part 1 of series 3, prompting Grounds to write his character Elvis's death into part 2 for added drama.