The footage seen between scenes of vehicles, Afghan soldiers, etc. were actually shot in Kandahar during the final combat deployment.
"Hyena Road" actually exists and was known as "route Hyena". Several of the background stories the characters tell actually did happen during the construction of the route (e.g. an engineer did lose his leg below the knee as told by 39A near the beginning of the movie).
Partly filmed at CFB Shilo in Manitoba, and partly in Jordan.
Nanawatai (Pashto: "sanctuary") is a tenet of the Pashtunwali code of the Pashtun people. It allows a beleaguered person to enter the house of any other person and make a request of him which cannot be refused, even at the cost of the host's own life or fortune.
It wasn't mentioned in the movie, but Route Hyena was designed and constructed by the American army engineers of the 864th Engineer Battalion's 557th Engineer Company as a part of the Canadian Task Force Kandahar's mission. While American soldiers provided the actual construction labor, Canadian contracting officers mobilized up to 300+ dump trucks a day to maintain a "300m per week" construction rate. The Taliban caused significant delays and constant fear among the civilian drivers shooting them from the adjacent grape fields and opium fields.