All seven members of the massively popular K-pop group BTS have completed South Korea’s mandatory military service.

In South Korea, all able-bodied men aged 18 to 28 are required by law to perform 18-21 months of military service under a conscription system meant to deter aggression from rival North Korea.

BTS — short for Bangtan Sonyeondan, or “Bulletproof Boy Scouts” in Korean — debuted in June 2013 under the company Big Hit ...