SEOUL — South Korea’s parliament impeached acting President Han Duck-soo on Friday over a short-lived martial law, plunging the country deeper into political chaos, as the Constitutional Court said it would swiftly trial suspended President Yoon Suk Yeol.

The impeachment of Han, who has been acting president since Yoon was impeached on Dec. 14 for declaring martial law on Dec. 3, has thrown South Korea’s once-vibrant democratic success story into uncharted territory.

The motion led by…