What has been the role in world history of pastoral peoples in general and the mongols in particular?

- Produced agriculture where no one had thought possible.
- Played roles as traders and bandits on long distance trade routes. 
- Played roles in the the collapses of the 2nd wave civilizations and their rebuilds. 
- Supported Buddhism in China 
- Nomadic Bedouin Arabs aided in expansion of Islam. 
- Turks carried Islam to new lands. 
- Mongols made largest empire of the time. - Facilitated closer connections across Eurasia. 
- Increased the rate of technology & crop exchange, mixing of peoples, spread of epidemic disease. 
- Mongol tolerance of other religions facilitated spread of religion.