Why do K-pop stars like BTS have to complete military service – and which male idols will be next to enlist?

BTS’ Jin and Exo’s Suho, Baekhyun, Chanyeol and Chen will have to enlist before the end of the year, while Suga and Shinee’s Taemin are up in 2021 – which other K-pop idols will have to do Korean military service next, and is there a way to avoid doing it?
South Korea currently has one of the longest and strictest military service periods in the world. Since the law was introduced in 1957, when a Korean man turns 18 he is immediately enlisted for “first citizen service” and is liable for military duty. Upon turning 19, he is then required to undergo a physical exam that determines his suitability for military training. Those who are found to be healthy enough physically and psychologically can be enlisted for active duty, supplemental or second citizen service, depending on their qualifications, educational background and age. However, men who are found to be incapable of performing military service due to any disease, mental or physical incompetence, are exempted from mandatory service.
And how long can they put it off for? Eligible Korean men must enlist for duty before they turn 28 at the latest.
Usually, men serve in the army, marine corps, navy or air force for a minimum period of 18 to 21 months. After completing this period men are listed on the reserve roster and are obliged to attend three days of annual military training for six years.
Idols enlisting in 2020 and 2021
As we approach the middle of the year, fans are anxiously awaiting their favourite idols’ inevitable enlistment. Male idols born in 1992 will all be entering the military this year and some have already joined, such as Winner’s Lee Seung-hoon and Kim Jin-woo, a “91-liner” (born in 1991).
Nine-piece boy band Exo have begun the painful process of sending their members off for military service one-by-one, with Xiumin and D.O. enlisting last year. Their 92-line consisting of Suho, Baekhyun, Chanyeol and Chen, may enlist this year, with Suho being first.