A main supply route (MSR)[1] is the route or routes designated within an area of operations upon which the bulk of traffic flows in support of military operations[2] and humanitarian operations.[3][4] MSR is a term that is also used in insurgency and irregular war scenarios.[5]
Because of the intense and predictable flow of constrained military traffic MSRs can often become targets for opposing forces, as was the case with the Airport Road in Baghdad, a short but dangerous route.[6]