The U.S. Air Force awarded a mysterious contract to an Israeli firm for equipment to counter small drones like the ones used by Islamic State militants in Iraq and Syria.

But service officials will not disclose the type of system and whether it uses electronic jamming, conventional missiles, a combination of both, or some other method to down enemy drones.

Here’s what we know: The Air Force awarded ELTA North America Inc. — a U.S. subsidiary of Israeli Aerospace Industries — a $15.6 million contract for “counter-unmanned aerial systems.” The contract announcement specifically references “21 Man Portable Aerial Defense System kits,” which will be delivered by July 28.

Man-portable air-defense systems, or MANPADS, are shoulder-fired missiles traditionally used to shoot down aircraft. So was that what was purchased? Not so fast.

The system was purchased by the Air Force Life Cycle Management Center at Hanscom Air Force Base in Massachusetts. The organization at the base oversees communications and electronics purchases, which would hint the deal is likely for some some type of jamming system that can take down the small drones without firing a shot.

It just so happens IAI has been at international trade shows touting such a system called “ Drone Guard .” The system’s radars can detect, track and jam small drones. Last year, the company said it had sold Drone Guard to “several customers for critical asset and personnel protection,” but did not disclose the buyers.

The Air Force has several projects to counter small drones and is testing multiple technologies and systems, said Ann Stefanek, Air Force spokeswoman.

“Current Air Force efforts to counter hostile small [unmanned aerial systems] are primarily focused on non-kinetic options ranging in size from handheld technology to larger stationary and mobile systems that can be operated on the ground or in the air,” she said. “Although the primary focus of the service's efforts are non-kinetic, kinetic options to defeat small UASs are also being explored.” So, that could mean missiles and things that shoot drones out of the sky.

The Air Force is planning to have a formal program for countering small drones on the books by the end of fiscal year 2018, Stefanek said.

We know the Defense Department considers the system purchased this week so important it gave ELTA a no-bid contract. Pentagon officials consider the buy a “Joint Emergent Operational Need,” meaning it is a response to a problem on the battlefield that requires fast-tracking through the acquisition system.

firing up at a drone before it drops a bomb, outside western Mosul. the drones just keep coming pic.twitter.com/H1j2KMG3j6 — Mike Giglio (@mike_giglio) February 23, 2017

ISIS has relied on a wide variety of drones to defend its stronghold in the Iraqi city of Mosul — largely “commercial off-the-shelf drones to observe and drop explosives on the Iraqi security force and civilian positions ,” coalition spokesman Col. John Dorrian said in early February. As Iraqi troops pressed into the city’s western half this week, ISIS drones have remained a constant factor, drawing firing from Iraqi troops advancing on the city’s airport Thursday.

According to the group’s own media releases, ISIS carried out dozens of drone strikes already in the month of February. A former British Army officer, Nick Waters, gathered many before and after images of the strikes in an online gallery .

“Although dangerous and effective as a propaganda tactic, [ISIS use of armed UAVs] has limited operational effect on the battlefield and will not change the outcome or significantly delay the inevitable,” Dorrian said.

ISIS is not alone in operating armed off-the-shelf drones in the Middle East: Hezbollah did so in Syria back in August, and Hamas reportedly had one shot down by the Israeli Air Force along the Gazan coastline in September. But documents from the Mosul offensive show a serious approach to ISIS UAV operations — an effort that stretched to Libya , and grew to include “Management” and “Acquisition” departments, according to West Point's Combating Terrorism Center.