In 733, the empire under the Tang dynasty, which had previously been divided into 10 administrative regions called 'dao' circuits of inspection, was redivided into 15 dao circuits, each of which had a 'saiho shochishi' stationed.
開元20年（733年）に、それまで10道に区分されていた唐朝治下の諸地方を、15道に区分し直し、各道に採訪処置使を設置した。