Mongols favored trade even before Ghenghis khan, they hunted/herded very few were weapon makers or potters/weavers, many items they needed to living had to be traded. As Ghenghis khan rose to he realized the Mongol army was gonna need many things for battles. To facilitate trade Ghenghis offered protection to merchants that came from east and west, offered higher status for merchants allowed by the Chinese or Persians who despised trade and traders.
Hello,
The two groups that headed west were the settelers from america and the natives. They headed there to one explore and two for the amount of free land and gold.
The best historical skill is "though the eyes" of Roman Empire. In other words how did the Roman people react to brutal violence of hurting one another in battles of parties-of 2 sides.
Using this historical skill the historian would interpret the reasons as to why the Roman Empire could allow battle fights. In the eyes of Roman Empire:fighting for power, win, justice, challenge for the Empire -and prosperity.