How America’s Soldiers Fight for the Spectrum on the Battlefield

By Brendan I. Koerner

Dan Winters

An electromagnetic mystery in northern Iraq changed the course of Jesse Potter’s life. A chemical-weapons specialist with the US Army’s 10th Mountain Division, Potter was deployed to Kirkuk in late 2007, right as the oil-rich city was experiencing a grievous spike in violence. He was already weary upon his arrival, having recently completed an arduous tour in Afghanistan, which left him suffering from multiple injuries that would eventually require surgery. In the rare moments of peace he could find in Kirkuk, Potter began to contemplate whether it was time to trade in his uniform for a more tranquil existence back home—perhaps as a schoolteacher. Of more immediate concern, though, was a technical glitch that was jeopardizing his platoon: The jammers on the unit’s armored vehicles were on the fritz. Jammers clog specific radio frequencies by flooding them with signals, rendering cell phones, radios, and remote control devices useless. They were now a crucial weapon in the American arsenal; in Kirkuk, as in the rest of Iraq, insurgents frequently used cell phones and other wireless devices to detonate IEDs. But Potter’s jammers weren’t working. “In the marketplaces, when we would drive through, there’d still be people able to talk on their cell phones,” he says. “If the jamming systems had been effective, they shouldn’t have been able to do that.”

A self-described tech guy at heart, Potter relished the chance to study the jammers. It turned out that, among other problems, they weren’t emitting powerful enough radio waves along the threat frequencies—those that carried much of the city’s mobile traffic. Once the necessary tweaks were made, Potter was elated to witness the immediate, lifesaving results on the streets of Kirkuk, where several of his friends had been maimed or killed. “To see an IED detonate safely behind our convoy—that was a win for me,” he says. It was so thrilling, in fact, that when Potter returned from Iraq in 2008, he dedicated himself to becoming one of the Army’s first new specialists in spectrum warfare—the means by which a military seizes and controls the electromagnetic radiation that makes all wireless communication possible.

It is well known that America’s military dominates both the air and the sea. What’s less celebrated is that the US has also dominated the spectrum, a feat that is just as critical to the success of operations. Communications, navigation, battlefield logistics, precision munitions—all of these depend on complete and unfettered access to the spectrum, territory that must be vigilantly defended from enemy combatants. Having command of electromagnetic waves allows US forces to operate drones from a hemisphere away, guide cruise missiles inland from the sea, and alert patrols to danger on the road ahead. Just as important, blocking enemies from using the spectrum is critical to hindering their ability to cause mayhem, from detonating roadside bombs to organizing ambushes. As tablet computers and semiautonomous robots proliferate on battlefields in the years to come, spectrum dominance will only become more critical. Without clear and reliable access to the electromagnetic realm, many of America’s most effective weapons simply won’t work.

The Pentagon failed to foresee how much the wireless revolution would alter warfare.

Yet despite the importance of this crucial resource, America’s grip on the spectrum has never been more tenuous. Insurgencies and rogue nations cannot hope to match our multibillion-dollar expenditures on aircraft carriers and stealth bombers, but they are increasingly able to afford the devices necessary to wage spectrum warfare, which are becoming cheaper and more powerful at the same exponential pace as all electronics. “Now anybody can go to a store and buy equipment for $10,000 that can mimic our capability,” says Robert Elder, a retired Air Force lieutenant general who today is a research professor at George Mason University. Communications jammers are abundant on global markets or can be assembled from scratch using power amplifiers and other off-the-shelf components. And GPS spoofers, with the potential to disrupt everything from navigation to drones, are simple to construct for anyone with a modicum of engineering expertise.

Stateless actors aren’t the only—or even most troubling—challenge to America’s spectrum dominance. The greater an opponent’s size and wealth, the more electromagnetic trouble it can cause. A nation like China, for example, has the capability to stage elaborate electronic assaults that could result in nightmare scenarios on the battlefield: radios that abruptly fall silent in the thick of combat, drones that plummet from the sky, smart bombs that can’t find their targets. The US may very well never engage in a head-to-head shooting war in the Far East, but the ability to effectively control the spectrum is already becoming a new type of arms race, one that is just as volatile as the ICBM race during the Cold War—and one that can have just as big an impact on global diplomacy.

The American military is scrambling to develop new tools and techniques that will help it preserve its electromagnetic edge. But that edge continues to shrink by the day, and very soon our inability to completely control the spectrum might result in a different kind of war.

Any old crow will gladly tell you that spectrum warfare is nothing new. The men and women who go by that avian moniker, which derives from a World War II codename, are veterans of the American military’s decades-old efforts to attack and defend the electromagnetic domain. Their secretive trade dates back to the Russo-Japanese War: While facing an impending naval bombardment in 1904, a Russian telegraph operator used his spark-gap transmitter to jam the radio of a Japanese ship that was orchestrating the assault. Though this electronic gamesmanship worked wonders—the Japanese were unable to complete their bombardment—the czar’s military brain trust failed to learn from the experience. The following year at the Battle of Tsushima, Russian admiral Zinovy Rozhestvensky foolishly declined to jam his opponent’s radios, allegedly because he didn’t trust that his own transmitters would work. The Japanese, whose ships were outfitted with the latest Marconi wireless equipment, used their communications superiority to outmaneuver and destroy the majority of Russia’s Baltic Fleet.

Four decades later, during World War II, the advent of radar spurred both Axis and Allied powers to invent ways to cloak the true natures of their aerial exploits. One of the most famous innovations was Moonshine, a British system that absorbed, amplified, and then echoed German radar waves, so that a group of just a few planes could mimic an armada of hundreds. When the Cold War commenced, the US focused on refining and improving these early methods of electronic bamboozlement. During the latter stages of the Korean War, for example, American B-29 bombers were outfitted with primitive jammers that befuddled the radar on antiaircraft guns. And starting in 1965, Navy jets in Vietnam were equipped with torpedo-shaped jamming pods that knocked out early-warning systems with torrents of electronic noise.

“The next war will be won by the side that best exploits the electromagnetic spectrum,” a Soviet admiral observed in 1973, shortly after Israel used jamming techniques to outwit Syrian guided missiles during the Yom Kippur War. Clearly in agreement with that prognostication, the US Air Force spent a good chunk of the Reagan era developing the EF-111A Raven, an electronic jamming plane that would play a key role in shutting down Iraq’s radar stations during the early hours of Operation Desert Storm.

But after that emphatic victory, the American military lost interest in the Old Crows’ geeky specialty. This was due partly to a vogue for stealth technology: Since aircraft like the B-2 bomber were designed to evade radar by virtue of their sleek shapes, jamming equipment seemed superfluous. But the Pentagon also failed to foresee just how much the new millennium’s wireless revolution would alter warfare—by making unmanned vehicles pervasive and giving asymmetric forces new means to coordinate and execute attacks.

The folly of this strategic myopia became apparent soon after the 2003 invasion of Iraq. Insurgents quickly mastered the art of constructing radio-controlled IEDs, which they set off with a range of common gadgets—cell phones, of course, but also more basic devices such as garage-door openers and toy-car remotes. The Army lacked the technical expertise to prevent the insurgents from using the spectrum, so it turned to the Navy and Air Force for assistance. But those branches hadn’t done enough to update their spectrum-warfare capabilities over the preceding decade. Their jammers were designed to affect large-scale radar installations, not the narrow slivers of spectrum used by civilians. And much of this equipment was ancient: The Navy’s preeminent jamming pod, the ALQ-99, had debuted in the early 1970s and was plagued by reliability problems related to its age. (The ALQ-99 will remain the state of the art in the Navy’s arsenal until at least 2020, when it’s scheduled to be replaced by the yet-to-be-built Next Generation Jammer.)

When the Army finally began to equip its armored vehicles with hacked-together jammers, a new set of problems arose. The systems’ antennas blasted out radio waves with such reckless abandon that plenty of friendly communications links got zapped in the process—a problem that the military terms “signal fratricide.” These jammers were so unruly, in fact, that they often forced vehicle commanders to deal with a potentially lethal conundrum. “I had a choice as a guy driving down the road—do I want to communicate, or do I want to conduct a defensive electronic attack against a potential IED?” says colonel Jim Ekvall, chief of the Army’s Electronic Warfare Division. Wrong decisions led to lost lives.

Over time the Army learned how to fine-tune its jammers to target only the most worrisome portions of spectrum, rather than enormous swaths that included Americans’ preferred frequencies. To make this possible, soldiers known as spectrum managers created detailed maps of all of Iraq’s electromagnetic activity, a chore that required laborious intelligence work. In addition to tracking and recording the emissions of every piece of friendly military hardware, the managers had to compile a list of which frequencies were used by a galaxy of cheap civilian devices.

This mountain of data was incorporated into spectrum usage plans that likely helped reduce both signal fratricide and roadside bombings: Between June 2007 and June 2009, monthly IED attacks in Iraq decreased by 90 percent. The campaign’s success awakened the Army to the need to cultivate as many spectrum-savvy soldiers as possible. In 2009 it made electronic warfare a distinct career for enlisted soldiers, who could elect to study the craft in a new program at Fort Sill, Oklahoma. Jesse Potter, the master sergeant who helped solve the 2007 jammer mystery in Kirkuk, was among the program’s first graduates, thereby earning the right to wear a special insignia featuring a lightning bolt crossed with a skeleton key.

Master Sergent Jesse Potter, one of America’s first dedicated spectrum soldiers. Dan Winters

These newly minted spectrum warriors found that their skills were much in demand in Afghanistan, where the Taliban recovered from its initial defeat in part by learning how to hack mobile technology—not only to detonate IEDs but also to maintain communications while on the run. To stay in touch with one another in the nation’s hinterlands, Taliban operatives often extend the range of existing mobile networks. “They pay some guy 10 bucks and say, ‘Go climb up that mountain over there and put up this repeater,’” says Brian Filibeck, a chief warrant officer who picks candidates for the electronic warfare school at Fort Sill. Many Taliban ambushes were planned using those simple bundles of antennas and amplifiers.

US forces had to rapidly come up with solutions to this challenge. Tasked with dominating the spectrum in regions largely inaccessible to ground vehicles, the Army built Ceasar, a modified version of a Navy jammer that can be affixed to a C-12 Huron turboprop airplane. Ceasar can sense the emissions of the Taliban’s repeaters, then jam their signals. The Army is now trying to miniaturize the system so it can be loaded onto unmanned aerial vehicles such as the Gray Eagle or even the hand-launched Wasp.

The Taliban and its ideological brethren are constantly trying to improve their spectrum-warfare weaponry. Chief among their goals is to reduce the threats posed by American drones. In 2009, US forces discovered that Iraqi insurgents were using a commercial program called SkyGrabber to intercept video feeds from Predator UAVs. The software allowed the insurgents to use ordinary satellite dishes to capture data as it was being transmitted back to base; because the data was unencrypted, SkyGrabber was then able to convert it into watchable media files. The US has since begun encrypting the drones’ video feeds. But according to a classified report leaked to The Washington Post by NSA whistle-blower Edward Snowden and then published last September, al Qaeda is also trying to figure out how to sever the links between drones and their human operators, who can be stationed half a world away. One of the organization’s most promising lines of inquiry has involved the construction of GPS jammers, which could theoretically be used to corrupt a drone’s navigation and missile-guidance capabilities. Analysts with the Defense Intelligence Agency observed that such systems, if further developed, “probably would be highly disruptive for US operations in Afghanistan and Pakistan.”

The building that houses the army’s spectrum elite is fittingly tough to locate without help from GPS. The bland redbrick edifice is perched on a hilly corner of Fort Leavenworth, Kansas, far beyond the 187-year-old Army base’s horse stables and forested picnic area. From down below on McClellan Avenue, the place is easy to mistake for a dormitory or unusually dour day-care center. But the Electronic Warfare Proponent Office (EWPO) is actually a hotbed of classified activity, all geared toward building US spectrum dominance—an already difficult task that keeps getting harder by the year.

Life was much simpler for the Army back when ruling the skies, rather than the electromagnetic waves, was its chief prerequisite for success. Gaining air supremacy may require colossal amounts of fuel and bombs, but it’s easy to define and hard to overcome once established. When Army general Norman Schwarzkopf declared that coalition forces had secured total control of Iraq’s airspace just two weeks after the start of Operation Desert Storm, he was able to cite indisputable evidence: A significant chunk of Iraq’s air force had been annihilated, along with the aviation infrastructure that supported it. There was no chance that Saddam Hussein would be able to field a fleet of replacement MiGs in a matter of weeks.

Spectrum supremacy, by contrast, can never be more than fragile. For starters, it is tricky to ascertain when it has even been attained—there is no quick formula for evaluating when an enemy has been entirely ejected from an immense, invisible battlespace. More important, even a reeling opponent can rebound quickly in the spectrum: Launching an electromagnetic counterattack doesn’t require hundreds of millions of dollars’ worth of jets, just a handful of gadgets and some basic engineering skills. “For a warlord to go and get their hands on a piece of equipment that can create a huge communications black hole and create serious havoc, that’s very cheap, very realistic,” says Filibeck, one of the top officers with the EWPO.

As al Qaeda has discovered, waging do-it-yourself spectrum warfare against the US is not quite as easy as jamming a cell phone tower. American communications devices are fortified to resist elementary attempts at electromagnetic meddling. The next generation of military radios, for example, will feature an antijam mode in which signal power is automatically increased in response to perceived electronic threats. Yet weaknesses still abound, particularly in systems that use GPS data—notably the drones that now make up more than 40 percent of the US military’s aerial fleet. GPS relies on a technique called direct-sequence spread spectrum to fend off jamming. But DSSS, which involves the scrambling of data into hard-to-guess patterns, is far from foolproof. In early 2012, for example, when North Korea spent 16 days emitting signals from truck-sized GPS jammers, more than 1,000 South Korean aircraft reported feeling the effects. And that June a University of Texas at Austin team managed to hijack a drone by sending it counterfeit GPS instructions. Incidents like these recently spurred a Department of Homeland Security official to warn that “a single well-placed low-power GPS jammer or spoofer could disrupt an entire region [of the US].” (To prevent the smuggling of these devices, which are illegal in the US, the Air Force Research Laboratory is developing a jammer detector that can be installed at border crossings.)

Nor would it take much for even relatively unsophisticated enemies to develop those tools. “You can go onto the Internet and Google how to build low-cost GPS denial-of-service devices,” Jesse Potter says. “They’re about the size of a small computer. If an enemy can build a thousand of those and place them all over the battlefield so I can’t find them all, then I’ve got a problem.” One of those problems could involve an Army convoy suddenly losing its navigation and communication capabilities right as it’s crossing a perilous stretch of enemy-held territory—soldiers isolated in such a manner would be vulnerable to attacks from guerrillas who know the terrain. Or the enemy could snatch a drone out of the sky and crash it or even take it over.

And if an enemy truly lacks the technological wherewithal to pull this off? Then they can simply buy it. Plug-and-play jammers and electromagnetic analyzers are widely available for purchase, as are software packages designed to identify and defend against electronic threats on the battlefield. The Israeli firm Your Total Security, for instance, sells entire vehicles tricked out with all the gadgets necessary “to block a wide spectrum of radio and wireless communications frequencies.” And the French company ATDI offers HTZ Warfare, a “comprehensive radio planning solution” that promises to help forces avoid signal fratricide, intercept enemy communications, and repel attempts at jamming. A rogue nation equipped with this sort of technology could challenge American troops across the spectrum, hindering if not completely eliminating their ability to use their electronics during an invasion. And the road to Tehran or Bamako is a terrible place to lose every last bit of situational awareness.

With its time in Afghanistan finally coming to an end, the American military is in the early stages of the Pacific Pivot—a long-term strategy to counter China’s growing influence in Asia. The US is keen to deploy more troops to places like Australia and Guam, to station more Navy ships in Singapore, and to offer more cooperation to key regional allies such as the Philippines, all in the name of keeping pressure on the region’s heavyweight.

The nature of the geography in that sprawling part of the world, where strips of land are separated by vast expanses of water, will create fresh vulnerabilities in our military’s communications networks. “Things get much harder against Far East targets when we don’t have a dominating US military footprint in the region as we did with Iraq and Afghanistan,” says Charles Clancy, director of the Hume Center for National Security and Technology at Virginia Tech. “Command and control become even more exposed to attack, because we lack the resources on the ground to protect it. Also, without a physical footprint we rely even more greatly on unmanned systems.”

China is well aware that the Pacific Pivot will strain the US military’s ability to protect its networks against electromagnetic sabotage. The People’s Liberation Army is thus pumping tremendous resources into beefing up its spectrum-warfare operations, much as it has funded the formation of an elite hacker corps to wage cyberwar against its rivals. Thanks to this investment, the scientific literature now teems with Chinese-authored papers on topics like how to design better simulation software for aircraft that jams electronic signals. This research is supporting the development of devices that will make China our most formidable opponent in the spectrum.

Even if a full-on military confrontation is unlikely, there are still real benefits to gaining the technological upper hand. The ability to anticipate and counter an opponent’s weapons is valuable even if no attack ever comes—it gives a country leverage in the broader geopolitical sphere. And China is working hard to gain this leverage through the electromagnetic realm.

The Battle for Spectrum

The US armed forces still enjoy supremacy in the air, on land, and at sea. But maintaining control over the electromagnetic spectrum is now just as important as dominating these physical arenas—and increasingly harder to do. Keeping communications, navigation, and precision weapons working requires winning a cat-and-mouse game of jamming and counterjamming. —Katie M. Palmer

Low-powered Civilian devices Insurgents on the ground use cell phones and other remote-control devices to detonate IEDs. Those signals can be shut down by vehicle-mounted jammers — but a jammer that doesn’t target the right part of the spectrum won’t work and may even interrupt the military’s own communications. Radar Jamming

To frustrate an enemy’s radar, the US Navy relies on a jamming pod called the ALQ-99. But it dates to the Vietnam War and has many failings, including an unruly frequency generator that can interfere with friendly comms. The Navy’s Next Generation Jammer won’t be ready until 2020. On-ground and ground-to-air communication

Soldiers use the radio spectrum to coordinate attacks, to warn one another of ambushes, and to call in precision airstrikes. But these comms can be jammed by simple devices that flood the spectrum with electronic noise. The US military’s ability to identify and take out jamming sources is still limited. DIY mobile networks

Enemy forces with limited resources can dramatically improve communications by setting up simple, cheap repeaters to extend the range of mobile networks. The Army uses the aircraft-mounted, beyond-line-of-sight Ceasar jammer to intercept those communications and shut them down. Unmanned aircraft

In the past, insurgents have intercepted video feeds from UAVs using a program called SkyGrabber, and the US military has now begun encrypting these signals. It’s also theoretically possible for a spoofing attack to give a drone the wrong GPS coordinates and allow enemies to commandeer the aircraft. Precision weaponry

To hit their targets, guided missiles and artillery shells require radar or GPS, and the latter can be jammed or spoofed. GPS was built to resist attacks by modulating information across a range of frequencies, but there are always new ways to attack it, including targeting the satellites themselves. 

Dan Matutina

Some of its devices are designed to confuse guided weapons, which often rely on radar to home in on their targets. “We are now painfully aware of the jamming systems for their aircraft, some of which have the potential of making systems like air-to-air missiles inoperable,” says Richard Fisher, a senior fellow at the International Assessment and Strategy Center. There is every reason to believe that this technology could be adapted to bewilder active guided cruise missiles, a weapon essential to American naval might.

The Chinese are also working on ways they could, in a pinch, take out GPS, which would likely let them control the skies above Taiwan or the Korean Peninsula in the event of war. China’s fighters, bombers, and drones won’t suffer if GPS goes down: By 2020, the country will have completed work on Compass, its own 35-satellite navigation system. (Presumably, the US is working on a plan to jam it.) The US air fleet, by contrast, will be significantly handicapped without precise guidance from above. The Air Force takes the threat of a Chinese electromagnetic assault so seriously that it’s stepping up efforts to train its pilots how to fly without the aid of GPS, radar, or even radio communications. The Navy, meanwhile, is testing an antenna that will hopefully allow drones to quickly reestablish links with GPS satellites in the wake of a significant jamming attack.

But American airpower will not suffer alone if the Chinese win the battle for spectrum—ground power will also take a hit. Congress has mandated that two-thirds of the military’s ground vehicles be unmanned by 2025, and these machines are the ideal candidates to lead amphibious assaults along the Pacific Rim. But like aerial drones, ground-based drones will not be able to function without a dash of human guidance and a steady stream of navigational data. If Chinese jammers can overwhelm their systems, any robot vehicles racing up a beach in occupied Taiwan would simply fall idle.

In true Cold War fashion, Chinese-made spectrum-warfare technologies are likely to spread far beyond East Asia. “Everything that China manufactures is eventually offered for sale, up to and including nuclear weapons technology and ICBM technology,” Fisher says. “If they have a jamming system, it’s likely comparable or even superior to whatever alternatives are out there, and it’s likely to be sold.” The China Electronics Technology Group Corporation, a government-affiliated company that produces much of the nation’s spectrum-warfare hardware, is a fixture at major arms trade shows such as Peru’s Sitdef. If and when the US military is pulled into future missions in the steppes of East Africa or the forests of Central America, it may run into opponents armed with jammers that were manufactured in greater Shanghai. And if our military gets bogged down in those conflicts because it can’t dominate the spectrum to its liking, the Pacific Pivot will become significantly harder to pull off—much to China’s joy.

The orbit test bed looks vaguely ominous, like an interrogation chamber from an avant-garde sci-fi film. The room is cavernous and stark, with gleaming white floors and barren walls. The ceiling is lined with orderly rows of what look like upside-down Ikea standing lamps. Inside each hangs a yellow box emblazoned with the word winlab—the name of the Rutgers University laboratory where this curious array is located. The boxes, 400 of them in total, are radio nodes, all part of a robust network for putting experimental communications protocols and applications through their paces. Orbit is where wireless-technology researchers go to test new methods for sending data across cellular and wireless networks. It’s also where the US military hopes to find the algorithms that will tilt the spectrum-warfare playing field in its favor.

That precious code is emerging as part of the Spectrum Challenge, a tournament sponsored by the Defense Advanced Research Projects Agency. With $150,000 in prize money at stake, 18 teams are vying to create software that can recognize when radio waves are smacking into interference, then route them around the obstacles by adapting their waveforms and the frequencies they use. The challenge uses Orbit to host one-on-one clashes in which teams score points by successfully delivering packets of data from one end of the network to the other, a task complicated by the fact that competitors are allowed to jam one another at will.

“We first concentrate on denying the other team, then we try to push our trickle of packets through,” says Peter Volgyesi, head of the Vanderbilt University squad that won a $25,000 prize in a preliminary round last September. The jamming has been unexpectedly ferocious: Darpa was hoping that the winning team would be able to transmit 15,000 packets of data, but Volgyesi and his colleagues won the round by sneaking through just around 100 packets. In preparation for the tournament’s final round in March, the competitors are now modifying their code with an eye toward making it stronger and more agile; the algorithms need to be heavily redundant so information can still get through when faced with a barrage of electromagnetic noise. It’s a constant cat-and-mouse game in which opponents must try to outwit one another in new and innovative ways.

Darpa stresses that the Spectrum Challenge is primarily intended to elicit solutions to problems on the home front: With the American spectrum increasingly clogged by civilian traffic, the military is worried about interference around bases and testing grounds. But the tournament also has obvious implications for the future of combat. In a world where every opponent has the ability to conduct electronic attacks, the US knows that software is its one big advantage. If the challenge yields algorithms that can elegantly guide signals past jamming attempts, the American military will be immeasurably more confident in its future strategies.

The widespread adoption of tablet computers is one example of those plans. The Army recently awarded a $455 million contract for the development of ruggedized tablets, to be mounted in more than three dozen types of vehicles and weapon systems. Soldiers will rely on these computers to receive critical updates about the locations of threats or the movements of friendly forces. If those updates don’t arrive as intended because the Army’s mastery of the spectrum has been degraded, the results could be deadly.

Software will also help spectrum warriors do a better job of explaining their work to superiors. A big challenge they’ve faced is how to talk to commanders who know all about pounding targets with munitions but are puzzled by the abstractness of spectrum warfare. Jesse Potter jokingly disparages these officers as “meat eaters” who don’t readily process why their fortunes depend on the reliable transmission of radiation from one node to another.

This expository task should become easier in 2015, when the Army is set to roll out software that will create more user-friendly visualizations of the spectrum’s real-time status on the battlefield. Soldiers like Potter will be able to point out which locations are securely in American electromagnetic hands and which are susceptible to electronic attack.

Perhaps this effort will succeed in making the meat eaters understand the importance of spectrum. Perhaps the brains at the Electronic Warfare Proponent Office can keep a step ahead of their foes. If not, the US military will discover that no amount of firepower can assure its dominance.