Due to the many languages, accents and dialects used in the series, six separate dialect coaches worked with the actors to ensure accuracy, making sure for example that each character spoke the correct form of Arabic, be it Egyptian, Syrian or Tunisian. This particular care extended to post-production ADR and subtitling, which were checked, and re-checked.
Swiss actress Souheila Yacoub, who already spoke five languages fluently, spent two months learning Kurdish prior to filming. When sent to train with a Kurdish dialect coach on her first day on set, the coach thought she was being pranked and that Yacoub was actually Kurdish.
Due to real weapons being used on set in Morocco, with blanks, actors had to show their passports every day to the Royal Gendarmerie officers present to be handed their gun.
European interiors were shot in Belgium, exteriors in Paris, and Turkey, Syria, Egypt and Iran were all represented by Morocco and its High Atlas mountain range.
Each episode was filmed in 8 and a half days.