Who began forging an empire that eventually included China and Korea stretched into Russia and Eastern Europe and extended southwest as far as the Persian gulf?

The empire you are referring to was forged by Genghis Khan, the founder of the Mongol Empire in the early 13th century. Under his leadership, the Mongol Empire expanded rapidly, encompassing vast territories across Asia and into Eastern Europe, including parts of China, Korea, and reaching as far as the Persian Gulf. Genghis Khan's innovative military strategies and unification of Mongol tribes were key to this extensive expansion.