Final answer:
Yi Seong-gye seized power in Korea in 1392, founding the Yi dynasty and ruling as King Taejo.
Step-by-step explanation:
The military commander who seized power of Korea in 1392, founding the Yi dynasty, was Yi Seong-gye. After defeating Japanese pirates and opposing the Ming dynasty's attempted annexation of Korean territory, Yi Seong-gye took the opportunity to seize Korea's capital and gain control of the government. In 1392, he proclaimed himself the head of a new dynasty, the Joseon, and ruled as King Taejo.