Oops!

Didn't forget, just a bit lazy ...
1) This people were the first and only nation to officially convert to Judaism.
The Khazars. A nomadic tribe who conquered a great part of the plains and grasslands north of the Caucasus. Allies of the Byzantines and drove the Arabs back fr the Caucasus. Although many Khazars were Christians, the King decided to convert to Judaism officially.
2) This kingdom fought against the Chinese and the Khitans, then the Jurchens and finally succumbed to the Mongols.
Xixia. Or Hsi-Hsia in the older format. Tangut Tibetans formed this kingdom in the present Ningxia region in China, around the 'bend' in the Yellow River. IIRC Genghis Khan died after subduing this people.
4) This people provided the Mongol Yuan dynasty with heavy cavalry (i.e. knights, lances, armor and the like).
The Christian Alans of the Caucasian region. Originally sent to the Mongol Yuan court by the Ilkhans of Persia and Mesopotamia, a few thousand of these tribesmen was always camped with the main Mongol force. Formed the heavy cavalry portion of the Mongol army. (The Mongols were more like horse-archers).
8) This people were famous merchants along the Silk Road and thru out Central Asia.
The Sogdians (spelling?). Marco Polo would have known them. These Central Asians dominated the East-West trade betw Byzantine, Islam and the West and China.
9) This people instituted land reforms (namely giving land to peasants in return for military service) which would later form the basis of power for the Sui and Tang dynasties of China.
The Toba Wei, a tribe of uncertain extraction, possibly proto-Mongol. They slowly seeped into N China in the aftermath of the Han collapse and organized their lands into tight parcels of land, peasant fiefholders and obligatory military service, thus providing themselves with a strong hold on the land they held and reliable military manpower.