Organising the empire

After Genghis Khan's death the empire grew in two phases: 1236 to 1242, when Mongol armies under his grandson Batu took the Russian steppes, Kiev, Poland and Hungary and camped outside Vienna; and 1255 to 1300, when they conquered all of China (1279), Iran, Iraq and Syria. After the 1260s, expansion in the west stopped: family quarrels over succession mattered more than European campaigns, the Toluy branch poured its resources into China, and an understaffed Mongol force was defeated by Egypt.

Breaking old loyalties. Among the Mongols, every able-bodied man bore arms. Genghis Khan's army grew to include very different peoples, some who joined willingly (the Turkic Uighurs) and some defeated enemies (the Kereyits). He set out to erase old tribal identities:

• He kept the steppe system of decimal units (10s, 100s, 1,000s and about 10,000), but split up old tribes and clans and scattered their members across new units. Leaving one's unit without permission was harshly punished.
• The largest unit, the tuman (about 10,000 soldiers), now mixed people from many tribes, giving them a new identity linked to Genghis Khan.
• The units served under his four sons and specially chosen commanders called noyan.
• A new aristocracy was made of loyal followers: some honoured as anda (blood-brothers), others of humbler rank as naukar (bondsmen). Status now came from closeness to the Great Khan, not from being an old clan chief.

The four ulus. Genghis Khan gave each son an ulus, at first not a fixed territory but a share of a still-expanding dominion:

• Jochi, the eldest, the Russian steppes, stretching 'as far west as his horses could roam'.
• Chaghatai, the Transoxanian steppe and lands north of the Pamirs.
• Ogodei, named as the next Great Khan, with his capital at Karakorum.
• Toluy, the youngest, the ancestral lands of Mongolia.
• The sons were to rule together: each prince's troops (tama) were stationed in every ulus, and decisions about campaigns, plunder, pastures and succession were taken jointly at quriltais.

Keeping in touch. Genghis Khan built a fast courier system, the yam, with outposts at regular distances. To maintain it, nomads gave a tenth of their herds as the qubcur tax, which they paid willingly for the benefits it brought. Its speed and reliability amazed travellers and let the Great Khans keep watch over the farthest corners of the empire.

The cost of conquest. For conquered peoples the early campaigns were a disaster: cities destroyed, farmland laid waste, trade and crafts disrupted, many killed or enslaved. In Iran, the qanats (underground water channels) could no longer be maintained; as they crumbled the desert spread, and parts of Khurasan never recovered.

The Mongol peace. Once the fighting ended, Europe and China were joined in one territory. In this Pax Mongolica, trade along the Silk Route reached its peak, now running north to Karakorum. Travellers carried a pass for safe conduct (paiza in Persian, gerege in Mongolian), and traders paid the baj tax, all acknowledging the Khan's authority. From Genghis Khan's time, civil administrators were recruited from conquered peoples, sometimes moved across the empire (Chinese secretaries in Iran, Persians in China). The Chinese minister Yeh-lu Ch'u-ts'ai, the Juwaini family and the wazir Rashiduddin softened the harsher side of Mongol rule.