To get a cup of coffee at Gratitude Café, you’re going to need a heavily armed escort and the right paperwork. The tiny coffee shop is located in the U.S. Air Force’s Forward Operating Base Oqab (which means “eagle” in the Afghan language), a small compound of only a few acres surrounded by concrete walls and barbed wire in a corner of Kabul International Airport on the outskirts of Kabul, Afghanistan. It’s home to roughly a dozen senior-level officers and approximately 40 security personnel. Another 230 or so troops call it their home base, though they are housed nearby.

There are four checkpoints before you can enter the base. Two initial stops by Afghan forces involve complete credential checks and searches of individuals, their belongings and their vehicles. U.S. contractors paired with international partner forces, perhaps Jordanian or French soldiers, usually man the third checkpoint. That gets you onto the airfield, but you’re not finished yet. Finally, there’s a thorough once-over by U.S. forces before you can enter Oqab.

Once on site, you walk across the base’s assembly area, where the American flag is raised every morning and there’s a memorial to nine fallen soldiers who were killed in action. Eventually, you’ll find Gratitude Café, where you can enjoy a cup of freshly brewed coffee in the company of more firepower than you’ll see in an Expendables film.

Obviously, this is not your average Starbucks. The café is located in a revamped old connex — the military term for the corrugated metal shipping containers used for everything from living quarters to, well, coffee shops — with a deck built onto the front of it. It looks like a makeshift office on a construction site. The space inside is roughly 10 feet by 25 feet and eschews the fancy fixin’s of modern coffee shops. There are a couple of tables and a counter in the rear that holds the coffeemakers, espresso machines, electric kettles, various supplies and boxes of cookies, biscotti and other snacks. The walls are decorated with handmade thank-you cards and letters of appreciation sent to those stationed at the base.

Since this humble café opened in early 2014, it has been the home to a surprising social experiment created by now-retired U.S. Air Force Brigadier General John Michel, who was the base’s commander and the Commanding General of NATO Air Training Command-Afghanistan until last summer.

Gratitude Café is the exact opposite of an officers’ club. At this java joint, only senior leaders on the staff are allowed to work the counter. “We didn’t want to send a message that we built a coffee shop so the folks of a lower rank could serve us drinks when we came in,” says Michel. “We wanted to invert the concept. We wanted to say, ‘This a great opportunity to exemplify servant leadership.’”

Early every morning, a self-proclaimed den mother or den father, who volunteers to handle the overall management of the operation, walks over to tidy up the space, fire up the coffeemakers and run a custom-made Gratitude Café flag up the pole. “The concept is ‘Flag up, fuel up,’” says Michel.

This project bringing caffeination to up to 85 troops daily doesn’t cost taxpayers a dime. All the equipment, snacks, beverages and attendant materials — cups, stirrers, sugar packets, etc. — are donated by Americans back home. So service personnel may find themselves sipping on all kinds of coffees, ranging from mass-market brands like Starbucks and Dunkin’ Donuts to more artisanal roasts from M.E. Swings and Kicking Horse, depending on the latest haul. Nearly every day, packages arrive from the States after having made the two-week trip through the USPS and the Military Postal Service Agency. “Some people send boxes decorated so pretty we don’t even want to open them,” says Michel.

Michel purposely set up the supply chain to work this way. “People want to be involved in doing something for their service members overseas,” he says. “So how do you create an avenue that’s simple enough and has a low cost for entry? This is it.”

Contributors are sometimes given a shout-out on Twitter using the hashtag #GratitudeCafe (Michel boasts an impressive 512,000 followers on the social-media platform) or receive a handwritten note from one of the base’s senior officers. Extra-lucky donors might receive a star from a retired American flag that had been flown on a combat mission over Afghanistan.

One unexpected benefit of the café is that it created a casual space where Americans could meet with their Afghan counterparts — who generally choose tea over coffee. Since many formal interactions include a gift exchange, Michel and his senior officers began giving out the extra boxes of packaged baked goods, which were harder to come by and more expensive for Afghans to obtain. “We might look at a cookie or a cupcake and think, ‘That looks good,’” says Michel. “But it shows your desire to do something good for them. When they walk away with three boxes of Girl Scout cookies, it becomes a psychological, tangible reminder that this is a beneficial relationship that goes beyond all our day jobs. So I would look to see how big their pockets were when they left to gauge the success of an interaction.”

Anyone wishing to send contribute should mail goods — no monetary donations — to Gratitude Cafe c/o TAAC-Air/HKAIA APO AE 09320.