The 30-year-old posted a photo of himself with his new military haircut before enlisting on Tuesday. "It looks cuter than I expected," he said.
As South Korea is still technically at war with its hostile neighbour North Korea, all able-bodied men are required to serve in the army.
BBC reports Jin has begun five weeks' training at a bootcamp near the North Korean border.
After this, he will reportedly be assigned to a frontline unit. This news sent his millions of adoring fans into a frenzy.
So, what can Jin expect from his time on the frontline?
