How many Mongols lived during times of Chinggis Khan?

Mongols used a decimal system to organize themselves.

The nucleus of a nomadic system was one family. One ger-one family. Each family had to produce one solider. Ten families would form one unit, aravt. Ten aravts would be zuut, one hundred. Ten zuuts would be myangat. Myangat, or one thousand soldier was the main unit organized under a noble. So a noble would have a thousand families. A thousand families would conservatively be from 5,000–10,000 people.

Ten thousand soldiers, tumen, would be the biggest denomination. A khan who could produce tumen soldiers was a major force in the steppes. Not many khans had 50,000–100,000 people under him.

When Chinggis khan became the Great Khan of All Mongols, he separated his forces into three major units: Baruun gar (Western), Tuv (Central) and Zuun Gar (Eastern forces).

He put his faithful general Boorchi in charge of Baruun gar, Western Forces. Boorchi was responsible for four tumens. Around forty thousand soldiers and 200,000–400,000 people were under his command. This was further broken down to around 20 nobles who were in charge of myangats. Some Nobles had several myangats.

Mukhulai General became in charge of Eastern Forces, Dzungars. Dzungars had around six tumens, 60,000 soldiers. That’s around 300,000–600,000 people. Six tumens composed of around 20 nobles who were in charge of myangats.

Chinggis khan was in charge of the Central Forces. They consisted of four tumens. His mother and uncle became in charge of two tumens. Second son, Tsagaadai 8,000 families, third son Ugudei 5,000, youngest son Tului 5,000, brother Hasar 4,000, brother Alchidai 2,000, and Biliguudei 1,500 families.

This structure was not new. The Khunnus under Modun Shanyu had similar system of dividing forces under Westers, Eastern and Central commands.

Source: https://mn.wikipedia.org/wiki/%D0%A7%D0%B8%D0%BD%D0%B3%D0%B8%D1%81_%D1%85%D0%B0%D0%B0%D0%BD

Originally published at http://mongoliafaq.com on April 15, 2020.