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

South Korea's opposition-controlled National Assembly voted to impeach acting President Han Duck-soo despite vehement protests by governing party lawmakers, further deepening the country's political crisis.

South Korea's National Assembly impeached the country's acting president, Han Duck-soo, on Friday, marking the second time in December that it has chosen to remove the country's leader.