One Reaper stopped a public execution of ISIS prisoners in May using precision-guided munitions or PGMs. Other recent missions have included taking out senior commanders of the militant group.
"The most feared assets are the UAVs and the PGMs," said James Andrew Lewis, senior vice president at the Center for Strategic and International Studies, a Washington think tank. "That's the one that always has them (ISIS fighters) looking over their shoulders."
Also, Lewis said the use of special forces and intelligence assets have been meaningful elements of the coalition's war-fighting strategy. That includes an early effort to counter the problem of improvised explosive devices or IEDs.
"DOD has been pretty good at developing new approaches to meet whatever the current tactical problem is," said Lewis, a former official of the departments of State and Commerce who also advised the U.S. Central Command for Operation Desert Shield.
The Defense Advanced Research Projects Agency, or DARPA, also has been working on lower-cost technologies to help the military better fight insurgents. One example is DARPA's Persistent Close Air Support program, a tablet-based targeting and communication system that gives ground forces the power to ensure more precision air strikes.
At the same time, experts say the U.S. coalition fighting the Islamic State has been dealing with an enemy that has proven to be surprisingly organized and resourceful in its ways. For one, the terror group managed to make its own armored vehicles and to create weaponized drones.
Yet ISIS has lacked the basic technology of some established militaries, such as modern air defenses. As a result, it hasn't mattered as much if aircraft go low and slow and lower-cost precision weapon systems have proven effective, too.
"If all I'm doing is shooting up truck convoys or machine gun positions that ISIS has, I can do it with cheap but precision weapon systems," said Goure, a former Pentagon strategist. "I don't have to use things like Hellfires."
The Hellfire missile, costing about $110,000 apiece, is designed to defeat armored vehicles but also has proven useful in destroying key ISIS buildings. However, the military has been running out of the Lockheed Martin-made Hellfires and had to ask for special funding to replenish the supply.
Indeed, the Pentagon has been ordering a roughly $30,000 rocket known as the Advanced Precision Kill Weapon System from BAE Systems for use by coalition aircraft fighting ISIS in Iraq and Syria. Last year, the Defense Department awarded BAE a contract worth more than $600 million for the laser-guided system, which is an upgrade from a 2.75-inch rocket system first used decades ago.
According to BAE's website, APKWS was "developed as a highly cost-effective solution that leverages the military's existing infrastructure and inventory – and inspired by real combat challenges." It also touts the precision weapon having "a better than 93 percent hit rate."
Defense experts say another reason for the smaller weapons is they can be more precise, offer more flexibility and there's less collateral damage.
Another example is the AeroVironment's Switchblade drone missile, which was first used by U.S. forces in Afghanistan and then against ISIS in Iraq. The drone missile is launched from a tube on the ground and has cameras to allow the operator to isolate targets with lethal accuracy.
"With Switchblade, AeroVironment's been able to put into the backpack of the front-line war fighter the ability to deal with those lethal threats, quickly, reliably and effectively — and to do so without incurring collateral damage to noncombatants," said Steve Gitlin, vice president of corporate strategy at California-based AeroVironment.
Then again, a report this week by the group Airwars charged coalition civilian casualties have doubled under President Donald Trump. A March 17 air strike in Mosul killed more than 100 civilians but a Pentagon report in May concluded ISIS had booby trapped the building and put snipers there.
"Avoiding civilian casualties has been a major focus of U.S. policy going after terrorists and has driven a lot of restraint," said Paul Scharre, director of the technology and national security program at the Center for a New American Security, a Washington think tank. An ex-Pentagon official, he's also former Army Ranger who served on special operations missions in Iraq and Afghanistan.
There's also been more interest from the U.S. military in countering explosive-laden drone threats from ISIS as the terror group gets more inventive using off-the-shelf technology. The Islamic State fighters also have been using drones for reconnaissance purposes.
Anti-drone countermeasures are a growing area both on the battlefront and in the homeland. One anti-drone system is known as DroneDefender, a rifle-looking device used to disrupt the signal between the flying craft and operator.
"Market interest continues to be very high as drones/UAVs become more proliferated across the world and modified for deleterious purposes," said Katy Delaney, a spokesperson for Battelle, maker of the DroneDefender. She said the company has sold a total of around 200 of the DroneDefender units, including customers such as the DOD and U.S. Department of Homeland Security.
Competing anti-drone systems include the so-called DroneBuster weapon from Radio Hill Technologies and another product sold by the North American division of Israel's ELTA Systems.
On the aircraft front, there's now more interest in light-attack and armed observation planes with "off-the-shelf" technology as an option for missions where more expensive craft may not be necessary. Lower cost planes also would ease the burden on the Air Force's aging fleet of aircraft where readiness is often cited as a major problem due to maintenance issues.
"We're actually at the place right now where our F-18 fleet is severely overused and flown," said Scharre. "We're having to spend quite a bit of money to recapitalize that fleet."