A diplomatic courier is a U.S. government official who is trained and credentialed by the Secretary of State to accompany classified materials across international borders. The Diplomatic Security Service has approximately 100 diplomatic couriers who ensure secure delivery of classified and sensitive materials between U.S. consulates and embassies and the State Department.
None Swifter Than These: 100 Years of the Diplomatic Courier Service
Historical Timeline of U.S. Diplomatic Couriers
A Brief Diplomatic Courier History