Tumen

Tumen or Tümen ("unit of ten thousand"; Түмэн, Tümen ) was a part of the decimal system used by Turkic and Mongol peoples to organize their armies. Tumen is an army unit of 10,000 soldiers. Tumen was incorporated into the Mongolian language from the Uyghur language and is also used in the Mongolian language as another word for "very many".

The word "Tumen" was established by Mete Khan in the memory of his father, Touman.

Genghis Khan's organization
In Genghis Khan's military system, a Tumen was recursively built from units of 10 (Aravt), 100 (Zuut), and 1,000 (Mingghan), each with a leader reporting to the next higher level. Tumens were considered a practical size, neither too small for an effective campaign nor too big for efficient transport and supply. The military strategy was based on the use of tumens as a useful building block causing reasonable shock and attack.

Magyar military organization of the Conquest Era
This same kind of military organization was used by the Magyars during the Conquest of Hungary. According to Ahmad ibn Rustah (c. 930), a Persian explorer and geographer, the "Magyars are a race of Huns and their king rides out with horsemen to the number of 10,000 and this king is called Kanda".

In modern armies
Tümen is a military unit which is still used in the Turkish Army, consisting of 6,000 to 10,000 soldiers. Its commander is a tümgeneral in the Army and Air Forces and a tümamiral in the Naval Forces. It is the equivalent of a modern Division.