Air Force Lt. Col. Sean Hackbarth expects Tuesday to be mostly a normal day. He plans to report for work at the Federal Aviation Administration, where he’s a military liaison, and commute home to Northern Virginia when the day is done.

Except that if someone asks or he decides to tell, Hackbarth can finally talk freely about his significant other. They’ve been together for nine years — and his name is Mike.

After almost 18 years, the Pentagon plans Tuesday to formally repeal the ban on gays in uniform, known as “don’t ask, don’t tell,” permitting troops for the first time to publicly reveal that they’re gay without fear of official retribution. Enlistees who tell military recruiters, and troops discharged under the ban who are eager to reenlist, will be eligible to join up if they are qualified. And the Defense Department says it will have zero tolerance for anti-gay behavior, as it does for religious, racial and gender discrimination.

For Hackbarth, 44, the repeal presents long-awaited opportunities. He can finally tell one of his male co-workers the real reason he wants him to stop making gay jokes.

“It’ll be an eye-opener for him when I can turn to him and say, look, this is the situation, and I don’t appreciate any of it,” Hackbarth said.

And he can stop playing what gay troops call “the pronoun game” — referring to a fictitious “she” or “her” in his life.

Hackbarth’s 22-year military career almost ended in 1996 when an angry former boyfriend threatened to out him to commanders.

Scared, Hackbarth alerted an officer in hopes of avoiding a discharge.

“All I said was that my roommate was threatening me, but I think he understood the situation without me having to be explicit,” Hackbarth said. “The commander said: ‘You’re part of a team. Don’t worry about it.’ ”

But the military has discharged more than 13,000 service members since late 1993 for violating the ban. Backers considered it necessary to avoid potentially fatal battlefield distractions, but opponents panned it as a waste of resources that ended the careers of troops providing critical battlefield skills.

President Obama, who opposes the ban, began at the start of his term to work with military leaders to end it. In December, after a tumultuous two-year legislative campaign, he signed a measure that would repeal the policy once Pentagon brass certified that the military was ready. Over the summer, Obama and military leaders agreed to end the ban in late September.

The change comes as thousands of troops continue to serve in Iraq and Afghanistan, and gay troops repeatedly expressed concern about partners left behind with little support from the military.

Stephen Peters, who was kicked out of the Marines for violating the policy, is one of those partners being left behind. He lives outside a California military base with a Marine officer who is preparing to deploy to Afghanistan.

Once his partner goes, Peters, 31, is essentially on his own: He can’t visit the base without a visitor’s badge or enjoy discounts at military grocery stores because the federal Defense of Marriage Act bars the military’s official recognition of same-sex partnerships. Most troubling for Peters, he’s officially barred from the military’s network of spousal support groups.

“There’s still the apprehension of the fact that we have to deal with these issues without the support that other military families get,” Peters said. “We’re kind of left out on our own.”

Peters and his partner, who is still too nervous to be identified, said the legal barriers are causing additional strain on a relationship taxed by the deployment.

“Hopefully, it makes you stronger, but it would be a nicer world if all that stuff wasn’t there and we just had to deal with the other strains of one being in the military and one being the partner,” the Marine officer said.

But he’s already told his unit commanders that if he’s injured or killed, they need to call Peters.

Hackbarth’s partner, Mike Culver, 46, is also seeking broader changes.

“I’m not looking for widespread social acceptance,” said Culver, a former Air Force engineer. “I’m looking for the ability to walk in and unplug the breathing machine one day if I have to.”

And though Hackbarth expects a relatively positive response in the coming days, “I’m still fearful of retribution,” he said. “I’m not entirely sure how this will be accepted or received, but I think it’s important to do.”

That fear among some hasn’t overshadowed the eagerness with which gay rank and file troops, senior officers and their partners look forward to Tuesday’s formal repeal. Gone will be the days of showing up at a military barbecue and introducing a gay partner as a “roommate,” “high school buddy” or “family friend.” They won’t have to sit silently through a colleague’s homophobic rants. And being able to talk openly to fellow troops on the battlefields of Iraq and Afghanistan about missing a gay partner back home should help erase what some described as an almost crippling stress during previous deployments.

Hackbarth and Culver plan to attend parties with other gay and lesbian troops and veterans to celebrate Tuesday’s achievement. Similar festivities are planned at bases and veterans’ halls around the world. In Washington, Obama administration officials said written statements marking the day are all that are expected from the White House and Pentagon.

But for Hackbarth and Culver, Tuesday changes so much about their lives. It means, for example, finally sharing personal anecdotes with colleagues who don’t know their whole story.

“It’ll be nice to have it be easier and do things like put pictures of your partner on your desk,” Hackbarth said.

The couple met while studying at Alabama’s Maxwell Air Force Base and managed to shield the relationship from colleagues as they moved across the country.

During dual assignments at the Pentagon, one of Culver’s assistants also worked with Hackbarth but had no idea the two men knew each other. Try as they might to avoid awkward introductions, they once ran into her while walking together in Crystal City.

“She smiled and walked on” and remains one of the couple’s closest friends, Hackbarth said.

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