In the wake of 9/11 on an American military base in South Korea, then-Army Staff Sergeant Dave Yeager sat down at a slot machine operated by the Defense Department and made what he now calls the biggest mistake a budding problem gambler can make: He won.

“All that stress, all that tension, all the things that I was carrying with me in that moment went away,” Yeager told CNBC.

What was supposed to be entertainment, a way for servicemembers to relax, instead for Yeager grew into a disorder that would cost him his career, his financial security and his family.

“It went from, I was have fun doing this, to, I have to do this. It became an obsession for me,” he said.

In his book, “Fall In: A Veteran with a Gambling Addiction,” Yeager wrote about how he borrowed from subordinates, stole from petty cash and left his family in a lurch financially. Such vulnerability in a servicemember affects individual readiness and potentially even national security, if enemies were to exploit it, he pointed out.

Yet, when Yeager said he confessed of that vulnerability to his commanders and his counselors, no one pointed the finger at his gambling, or helped him to help himself.

“The chaplain told me to go to bingo night on Sunday. That would give me something to do,” Yeager said. “And I’m like, ‘I think you’re missing the point here.'”

As of 2017, the Department of Defense operated more than 3,100 slot machines on U.S. military installations in a dozen foreign countries, according to a report from the Government Accountability Office. The machines produce more than $100 million annually in revenue and is seen as a morale booster for the welfare and recreation for servicemembers akin to activities like golf, libraries and other entertainment.

Overseas, servicemembers as young as 18 may be permitted to gamble.

Domestically, slot machines are prohibited on military bases, though casinos are frequently located nearby. There are seven local casinos located within 20 minutes from Joint Base Lewis-McChord in Washington state, one of the country’s largest military installations.

In 2018, when a Supreme Court decision paved the way for states to legalize sports betting, the opportunities for wagering exploded. Now, more broadly, all but four states permit gambling in some form.

“All of a sudden, we started to see a lot of people with gambling problems calling and asking for some help, usually within a year or two from the time that it expanded,” said Heather Chapman, a clinical psychologist and director of the national gambling treatment program for the Department of Veterans Affairs.

Diagnoses of pathological gambling disorders among servicemembers and veterans is soaring, with more patients receiving a diagnosis in the first half of 2024 as in all of 2022, according to VA research. Twenty percent of those referrals are women.

“It’s not terribly surprising, because with accessibility and availability increases, we tend to see a rise in unhealthy engagement,” said Dominick DePhilippis, deputy national mental health director for substance abuse disorders for the VA.

Servicemembers are more vulnerable than civilians to gambling disorders and may be hesitant to self-report, fearing they could lose their security clearance or to avoid the stigma attached to gambling problems, the VA research found.

Studies have found the prevalence of problem gambling and gambling disorder among veterans to be as high as 10.7% in some parts of the U.S., the department said, though those studies have been smaller and typically regional, which leads to a wide variance among results.

To address the growing concern, the VA operates two residential treatment facilities for gambling addiction and has a myriad partnerships with civilian facilities throughout the country, Chapman said.

“We are sort of the mecca of gambling treatment,” she said.

The VA began treating gambling disorders in the late 1960s, about nine years after Congress banned slot machines from domestic bases.

The Department of Defense declined CNBC’s request for an interview, but said in a statement there hasn’t been any systemwide increases in resources to address problem gambling. It said a Health Related Behavior survey from 2018 — before the boom in sports betting — indicated that rates of problem gambling among servicemembers of 1.6% to 1.7% was in line with the incidence in the civilian population.

“DoD researchers are aware of changes in gambling availability due to new mobile and sports gambling options and will consider these variables in future military gambling research,” a department spokesperson said in an email.

The military is conducting a new survey, with results expected in the fall, the spokesperson added

Servicemembers are now screened for gambling disorders every year during their health physical after a provision signed into the National Defense Authorization Act by then-President Trump. And the Department of Defense said that servicemembers with a gambling problem will not be penalized for obtaining treatment after being screened.

Policies around education are largely decided by individual commanders and vary widely from base to base.

Brianne Doura-Schawohl, the wife of a Coast Guard officer and a lobbyist for responsible gaming, wants the Defense Department to implement gambling education and treatment policies that apply across the entire military.

“These policy manuals need to be updated to address this addiction, the way they address things like alcohol. We need to be doing more to prevent and treat this disorder,” Doura-Schawohl said.

“I believe that the men and women who put on that uniform every day are willing to sacrifice it all. I think the least we can do is have the government tell them we’ve got your back,” she said.

Unlike U.S.-based casinos, the DOD is not required to provide educational materials or resources on how to get help for a gambling problem, according to a spokeswoman for the the National Council on Problem Gambling.

“NCPG believes that those who profit from gambling – including DOD – have an ethical and economic obligation to utilize some of those profits to mitigate gambling-related harm,” the organization said in a statement.

Sens. Elizabeth Warren, D-Mass., and Steve Daines, R-Mont., introduced legislation in 2018 called the Gambling Addiction Prevention Act (GAP) that sought to require the Department of Defense to track gambling disorders as well as implement policies and programs to treat gambling problems among servicemembers. It failed to gain traction.

More recently, Rep. Paul Tonko, D-N.Y., proposed an amendment to the most recent National Defense Authorization Act to curb all gambling on military bases, though it was not included in the final legislation.

“Our brave service men and women sacrifice everything to protect our nation and its freedoms. We must do all we can to support them by confronting problem gambling head on and ensuring this known addictive product is treated with the seriousness and precaution that we do with other addictions,” Tonko said in a statement to CNBC.

Around patriotic holidays like the Fourth of July, many casinos and sportsbooks send targeted promotions to servicemembers and veterans.

At Pahrump Nugget and Lakeside Casino in Nevada, Golden Casino Group offers “Military Mondays,” where veterans and active duty military can win free slot play just by swiping their card.

Some casinos offer veterans their own military-themed membership card based on their service. For example, Penn’s Heroes program offers rewards and promotions “for those that have given more.”

Caesars’ Rewards Salute Card “shows their appreciation” to active-duty military members and veterans by rewarding them with credits and free play offers, though the company said every rewards member is able to convert rewards into free play.

“We are not giving veterans easier access to or any additional free play offers,” a company spokeswoman said.

MGM Resorts has decided only to offer non-gambling promotions targeted to the military and veterans. It is also helping to fund clinical research about gambling disorders among the military community.

BetMGM, a joint venture with Entain that has a veteran heading up its responsible gambling initiatives, has opted not to target military members or veterans with any promotions.