As the title says, how was the nomadic horse culture brought over to the Mongols? Was it peaceful trade over the centuries, conquest, assimilation by other peoples?

Did they acquire the horse culture after contact with the Indo-European steppe nomads who migrated to Central Asia and western Mongolia such as the Andronovo cultures, Scythians and Tocharians? Or was it a later influence by (proto) Turkic peoples that gave the Mongols their horses based culture and war strategies? Was Metallurgy introduced around the same time to the Mongols as well?

Bonus points if you answer the same question for Turkic people.

Thanks in advance!