SEOUL, South Korea — The army lieutenant knew his career was irrevocably damaged when military investigators visited him in 2017, demanding that he admit having had sex with another male soldier — a crime in South Korea’s military.
When the investigators put him on a video call with his ex-lover, who admitted to the relationship, he felt he had to confess. Then they seized the lieutenant’s smartphone, pressing him to identify gay soldiers in his contact lists. And they humiliated him with questions like “What sex positions did you use?” and “Where did you ejaculate?”
The lieutenant — who in an interview asked to be identified only by his surname, Kim — could have gone to prison, but his indictment was suspended because of his “contrition.” He chose to leave the army, though, believing that he no longer had a future there.
South Korea’s military says it does not discriminate against sexual minorities. But Mr. Kim is one of an increasing number of gay or transgender soldiers who have been persecuted under Article 92-6 of the Army Criminal Act, which has been used to out them and punishes them for consensual sex, Amnesty International said in a report released on Thursday.
Under Article 92-6, “anal sex and other indecent acts” between military personnel can be punished by up to two years in prison, even if they take place off base, while the soldiers are off duty and by mutual consent. Repeated attempts by advocates for L.G.B.T. and intersex people to abolish the law have been unsuccessful.
“South Korea’s military must stop treating L.G.B.T.I. people as the enemy” said Roseann Rife, East Asia research director at Amnesty International. The group’s report, “Serving in Silence,” also details sexual and other abuses inflicted on gay soldiers, or soldiers perceived as gay, by their superiors and their fellow soldiers.
“It is long overdue for the military to acknowledge that a person’s sexual orientation is totally irrelevant to their ability to serve,” Ms. Rife said.
The South Korean government says Article 92-6 is not meant to punish sexual orientation. Rather, it says, it is needed to deter sexual abuse in the army, which is almost entirely male. The country’s Constitutional Court has repeatedly ruled that the article is justified by the military’s need to preserve discipline and “combat power.”
South Korea, which technically has been in a state of war with North Korea for decades, has a conscript army of about 600,000 soldiers. All able-bodied South Korean men are required to serve for about two years.
The military says it does not bar gay and transgender people from serving, and the Defense Ministry has expanded training on protecting the rights of sexual minorities. What is forbidden, the army says, is not sexual identity, but what the law calls “indecent” sexual activity.
Enforcement of Article 92-6 has been on the rise. The number of soldiers charged under it went from two per year in 2009 and 2010 to 14 in 2012, then 28 in 2017. Ten soldiers were charged in the first half of 2018, the most recent period for which data was available.
Military veterans have long reported discrimination against homosexuals in the army, as well as more widespread abuses like beatings, hazing, and bullying. Most gay soldiers have hidden their sexual orientation for fear of being outed and harassed.
In 2017, the year Mr. Kim was interrogated, the army launched a particularly aggressive crackdown based on Article 92-6, confiscating soldiers’ cellphones without warrants and forcing them to identify other soldiers with whom they’d had sex, according to the Military Human Rights Center, a civic group based in Seoul, the capital.
Nine active-duty soldiers were indicted, of whom eight were convicted, including a captain who received a suspended prison term. Several of the cases are being appealed, and none of the soldiers have been sent to prison, according to Lim Tae-hoon, director of the Military Human Rights Center of Korea, which provides legal assistance for the soldiers.
Fourteen other soldiers were investigated but not indicted — some of whom, including Mr. Kim, has petitioned the Constitutional Court to rule Article 92-6 unconstitutional, Mr. Lim said.
In South Korea, which has been slow to embrace the rights of sexual minorities, that 2017 crackdown triggered an unusual degree of outrage.
In recent years, gay people have become more visible in the country. But conservative Christian groups have also escalated demonstrations against homosexuality in major cities, often calling gay soldiers a threat to military readiness.
Those groups helped to scuttle attempts in Parliament to pass an anti-discrimination law, urged on South Korea by the United Nations, that would give sexual minorities the same protections that other minority groups have.
Amnesty International’s report describes in vivid detail how antigay attitudes have translated into physical and sexual abuse within the military.
One former soldier told the rights group he had been forced to have oral and anal sex with another gay soldier, as a superior taunted, “Don’t you want to have sex with a woman like man?” Others have been sexually abused for “not being masculine enough,” walking in an “effeminate” way or having a high-pitched voice, according to the report.
Amnesty said it interviewed 21 former, current and future soldiers for the report, most of whom used pseudonyms, including Mr. Kim. One of them, Jeram Yunghun Kang, agreed to the use of his full name in an interview with The New York Times.
Mr. Kang, who joined the army in 2008, said other soldiers in his unit harassed him by groping him, kissing his neck and pulling down his underwear. After he confided to an officer that he was gay and asked for help, his battalion commander outed him in front of his entire unit, asking him, “Who did you seduce last night?”
From that day on, Mr. Kang said, he had to wear a “smiley face” pin on his chest, marking him as a “soldier of special interest.”
“I had to take showers alone,” Mr. Kang said by telephone from London. “I was considered dirty, someone neither male nor female who should not be naked in the presence of other men.”
Mr. Kang was eventually sent to a military psychiatric ward, where he was forced to take antidepressants twice a day. Staffers there advised him to pretend to be insane so he could be ruled unfit for service and expelled from the military.
Mr. Kang refused. Instead, he said, he attempted suicide twice. He was put in solitary confinement, his limbs tied to a bed.
“While I was tied there in a room where there was no sound or light allowed in, I felt that there was nowhere for me to run in South Korea,” he said. After 116 days in a hospital, he was expelled from the military in 2009 for psychiatric reasons.
Mr. Kang’s mother, who raised him alone, sold her house so he could go to London, to live and study in a more accepting environment. Since moving there in 2016, he has drawn on his experience in the military to create installation art and a self-published book.
Now, his student visa about to expire, Mr. Kang is afraid to come home.
“I left South Korea as if I were fleeing,” he said. “I dread going back there. I feel like I am a refugee.”
A version of this article appears in print on July 11, 2019, Section A, Page 9 of the New York edition with the headline: Gay Soldiers Can Serve. But They May Face Prison