A tenma refers to a transportation system from ancient times to the early modern times in Japan that carried envoys or goods, or to a horse used. About in the latter half of the seventh century in ancient times, the tenma system was improved as a system of transmission of information between the capital and local regions in the ritsuryo system. Subsequently, presumably from the tenth century on, the ancient tenma system went out of use, however, in the Middle Ages, lords of manors and jito (agents in charge of manors of their lords) began to post tenma (post horses) that shuttled between their residences and own domains. During the Sengoku Period (Period of Warring States) (Japan), warring lords posted shukuba (post stations) along highways in their domains and tenma that shuttled between their main castles and branch castles. In the early Modern times, the Edo bakufu (Japanese feudal government headed by a shogun) improved highways across Japan and posted tenma at each shukuba.
Transportation systems under the ancient ritsuryo system were generally known as ekiden-sei and classified mainly into three systems: Eki-sei, Tenma-sei and Den-sei. The Eki-sei transportation system being intended mainly for transmission of urgent information between the capital and local regions, ekiro (highways) from the capital and local regions and umaya (facilities for providing houses, foods, etc.) along ekiro were maintained, and informants, carrying an ekirei bell and using one of five to twenty ekiba (horses for transportation of official travelers) kept in an Umaya, passed through ekiro.
Unlike the Eki-sei system, the tenma system was mainly intended for envoys sent from the capital to local regions. A envoy sent from the capital to local regions, carrying a denpu (permit for using tenma) and changing tenma at each gunke (public office) that kept five tenma, reached his destination. Corresponding to his ikai (court rank), he was able to use a fixed number of tenma. The denpu had a carving showing the rank of the envoy. Envoys' lodgings, foods and so on were in charge of a gunke.
At first, the tenma system was presumed to have been a system to send an envoy with a special commission from the capital to local regions. For example, magishugyoku-shi (envoy), chugushoku-sokuto-shi, kenpaku-shi, runin (exiles), runin-kotori-shi and so on. However, from the early ritsuryo system, some cases of new kokushi (local governors) using tenma as a transportation means to their new posts began to appear, leading to the exclusive use of the tenma system by new kokushi going to their new posts by the early Heian period. The "Engi-shiki law" compiled in the early tenth century listed provinces where tenma were posted, which made it known that tenma were posted only along passing routes of new kokushi.
Place names including the word tenma still remain in various places where mainly modern tenmajo (post stations) were set.
(For details -> Denma-cho)