What the hell is hybrid warfare, anyway? While the other services increasingly fixate on China, “hybrid” is becoming the buzzword du jour in the U.S. Army, invoked even in Chief of Staff Gen. Ray Odierno‘s official “marching orders” to the service. But like “counterinsurgency” before it – and like “transformation” before that – the term is increasingly used and abused in bureaucratic and budget battles with little regard for what it might actually mean.

At its core, though, the concept is pretty simple, said one of the most influential thinkers on hybrid war, RAND analyst and retired Army Colonel David E. Johnson, in an interview with Breaking Defense. It’s the idea that there’s a deadly middle ground between “low-intensity” and “high-intensity” war, a class of threats whose weapons and tactics are a hybrid (hence the name) of guerrilla and great powers. It’s the idea that there are adversaries out there – Iran is the most prominent example – that are much more dangerous than the Taliban, but much more likely to actually fight us in the future than China is. It’s a tough problem, but it’s also one within the American military’s capacity to solve, if it relearns key skills and reinvests in key equipment neglected in the last decade of counterinsurgency. “Hybrid adversaries are not ten feet tall,” said Johnson, “but they require combined arms.”

The driver of the hybrid threat, for Johnson, is the spread of long-range weapons: anti-tank guided missiles, anti-ship cruise missiles, shoulder-fired anti-aircraft weapons (called “man-portable air defense systems,” or MANPADS), even relatively unsophisticated long-range rockets like those used by Hezbollah in 2006. When Israeli airstrikes alone couldn’t find and destroy the well-hidden rocket launchers, Israel sent in ground troops, only to be bloodied by unexpectedly fierce resistance.

The Israelis were trained for a guerrilla threat but unprepared for a hybrid one, argued Johnson, whose latest book, Hard Fighting (available free online), tells how the Israelis learned from their mistakes. With lightly equipped irregulars like the Palestinian groups Fatah and Hamas, which Israel had gotten used to fighting – or with the Taliban and Iraqi insurgents that the U.S. has focused on these last ten years – the threat is short-range weapons like roadside bombs, rocket-propelled grenades, and AK-47 assault rifles, able to reach out and kill somebody from at most a few hundred yards away. “They have to be in RPG and AK range because that’s all they have,” Johnson said. But against an adversary like Hezbollah, he said, whose sophisticated missiles threaten approaching tanks, helicopters, and even ships at sea, “it’s no longer a 500-meter problem, it’s a five-kilometer problem.”

In contrast to some other thinkers on future warfare, though, Johnson does not expect groups like Mexican drug gangs or even most insurgencies to acquire this kind of firepower. The global black market and events like last year’s looting of Libya’s arsenal of shoulder-fired anti-aircraft missiles mean sophisticated weapons are indeed available to bad actors, and the threat of a single terrorist incident rightly concerns homeland security authorities, he said; but staging a single attack is a long way from posing a battlefield threat. Just buying black-market weapons is not enough. “It’s not just having one or two, it’s also having supply chain and training,” Johnson said. “It’s not something you can figure out on YouTube.”

For an adversary to pose a hybrid threat, Johnson argued, a nation-state has to be involved somewhere, if only in the background. “Where can this happen? There are really two models,” he said. “One is a state decides to have a proxy and arms it, like Iran and Syria with Hezbollah, or like we did with the mujahideen [in Afghanistan in the 1980s].” Any confrontation with Iran would likely involve such hybrid proxies. “The other is a state melts down, and there are all these competing factions that were trained in the military and have weapons – like what happened in Chechnya [in the 1990s].” This meltdown model, he added, is the kind of hybrid threat that might emerge if the current crisis in Syria escalates, if the untested young dictator Kim Jong Un is overthrown in North Korea, or if a civil war erupts in ever-uneasy Pakistan.

So how can the US prepare for hybrid threats? In part by going back to the future, said Johnson, whose books include a history of how the US learned to use tanks and airpower in World War II. “It is a problem that can’t be solved by a single service,” he said. The Air Force and Army today work together more closely than ever before in providing air support to ground troops in Afghanistan, but air-ground cooperation has gotten good in past conflicts as well, only to break down post-war when bureaucratic and budgetary battles between the services start to matter more. Hybrid threats will impose serious limits on helicopter operations – as the Soviets found out in Afghanistan after the CIA provided the mujahideen with Stinger missiles – so support from higher, faster, and harder-to-hit fixed-wing aircraft will be essential. Conversely, the Air Force will need the ground troops to root out hybrid enemies from their hiding places, he argued, just as the Israeli Air Force proved unable to spot Hezbollah’s rocket launchers from overhead. “Ground maneuver is the only thing that will make him visible because he’s hiding from everything overhead,” said Johnson.

The Army will also need to rebuild its artillery branch for times when hybrid threats keep air support at bay, Johnson said. The artillery has had few targets for barrages in Afghanistan and Iraq, artillery staffs have frequently been repurposed as ad hoc hearts-and-minds cells, and artillery troops have been used as foot troops to assist the overburdened infantry. The resulting lack of training in core cannoneering skills led one Army report to call the artillery a “dead branch walking.” Said Johnson, “In brigades that are in Iraq and Afghanistan, the artillery battalion’s really a ground security force; in this kind of war an artillery battalion’s going to be an artillery battalion.”

Finally, to maneuver in the face of a hybrid enemy’s missiles, “armored vehicles are really important,” Johnson said. And he’s not just talking uparmored Humvees or MRAPs, which are relatively light wheeled vehicles with limited cross-country mobility and firepower: He’s talking tanks: fully-tracked, heavily armed, armored fighting vehicles like the M1 Abrams (pictured), the M2 Bradley troop carrier, and the proposed Ground Combat Vehicle. While some other experts argue that rapid advances in cheap anti-tank weapons make investing in new armored vehicles a losing proposition – notably a recent report by the influential Andrew Krepinevich – Johnson argues armor is still essential. “The IDF [Israeli Defense Force] realized that and built more Merkava IV tanks and is fielding the Namer APC [armored personnel carrier],” Johnson said. “What would Andy have one do against an adversary like Hezbollah? Are they a greater challenge than past state adversaries [like] Iraq that combined arms fire and maneuver was adequate to deal with?”

Airstrikes, artillery, tanks – all this sounds a lot like the Army that went into Iraq in 2003. Might the hybrid threat become the Army’s excuse to forget about counterinsurgency, just as it washed its hands of the messy guerrilla warfare business in the seventies and willfully unlearned the lessons of Vietnam? “We can’t say ‘thank God that’s over,’ like we did after Vietnam,” said Johnson, in part because it’s not: Guerrilla warfare isn’t going away, and even hybrid adversaries like Hezbollah often avoid airstrikes by hiding among the population, which makes dealing with the population an essential skill. “What we’ve learned in Iraq and Afghanistan certainly will be relevant in the future,” said Johnson. “It’s necessary but not sufficient, [because] there are other kinds of adversaries.”