With a newly shaved head, Jin, the oldest member of the Korean pop group BTS, began his 18 months of required military service on Tuesday. Jin turned 30 earlier this month. He begins five weeks of basic training at a camp about 45 kilometers from the border with North Korea. The training includes gun shooting, grenade throwing, and marching. A group of 20 to 30 fans, some holding Jin’s photos, and reporters gathered in the cold, snowy weather to see Jin enter the camp. A security force of about 300 police, military, and fire officials was there to provide security. He is so skinny, said Mandy Lee, a 30-year-old fan from Hong Kong. I want him to eat more and stay healthy and safe. The BTS official Twitter account later posted images showing Jin with other members, likely at the camp, with a message saying: “Our bro!! Have a safe service!! Love you.” One image showed members touching Jin’s shaved head. Under South Korean law, most able-bodied men are required to perform 18 to 21 months of military service. The law exempts athletes, classical and traditional musicians, and dancers who performed well in international competitions. But K-pop stars do not receive exemptions, even if they are famous worldwide.