[updated with quote from Army source] WASHINGTON: The battle over the Army’s Ground Combat Vehicle isn’t only about one war machine and what it may weigh (80-plus tons) or cost ($13 some million). It’s just one front in a larger war over the Army’s armored heart and its role in the nation’s strategy.

As budgets tighten and the military reorients from Afghanistan to the Pacific, the nation can get by with “substantially smaller ground forces,” said Andrew Krepinevich, the influential director of the Center for Strategic and Budget Assessments. A former Army officer himself, Krepinevich has repeatedly called for cutting the Army in favor of air and naval forces. In particular, he told Breaking Defense, out of all the Army’s various branches, “armor/mechanized infantry is certainly a bill payer.”

While some heavy forces are necessary insurance against the unlikely event of a major ground war, Krepinevich said, he estimated that the Army could safely cut its armored battalions by about 20 percent. Blitzkrieg-style ground campaigns are increasingly impractical in the face of modern smart weapons, he argued, so the Army need not invest heavily in forces to repell them.

“Where would we see a traditional invasion? Maybe in the Korean peninsula?” Krepinevich asked. But even there, “it’s not like 1950 where there are hundreds of thousands of North Koreans coming across the border,” he said, and the South is now wealthy enough to defend itself without US tank units on the ground. Instead, he argued, the Army should invest in missile defenses, cybersecurity, and other capabilities to support the Air Force and Navy in a long-range “AirSea Battle” against China or Iran.

Not so fast, said one of the Army’s most interesting observers. “Everything about AirSea Battle is wrong,” retorted Maj. Gen. Robert Scales, retired commandant of the Army War College. “We are not going to fight China, and should we ever do something that dumb, we are not going to fight them in a major sea battle; it doesn’t play to the equities of the PLA [People’s Liberation Army]. The idea of a Leyte Gulf on steroids is completely ridiculous.”

“After every [ground] war,” Scales told Breaking Defense, “every president says well we’ll never do that again, and we do. We always do. Why? Because the enemy knows what our weaknesses are.”

Like past enemies, from the Chinese forces in Korea to the North Vietnamese Army to the Iraqi insurgents, Scales argued, future foes will avoid confronting US air and sea superiority. Instead, they’ll seek to draw us into protracted ground wars, where armored vehicles are our troops’ best protection. Since World War II, “we’ve never run out of fighter planes, we’ve never run out of ships; we’ve always, always run out of infantry,” Scales said. “Nothing substitutes for mass and the ability to achieve decisive effects on land.”

This debate goes to the heart of how the largest armed service sees itself. Since 1940, when the Depression-gutted military scrambled to rebuild itself to face the Nazi blitzkrieg, the core of the Army has been its armored forces: powerful, mobile, and expensive units of tanks, armored troop carriers, self-propelled artillery on tracked chassis, and a host of support vehicles to haul all the required fuel, ammunition, and spare parts.

The controversial Ground Combat Vehicle is meant to replace the armored forces’ current infantry assault vehicle, the M2 Bradley, which is heavily armed but — as Iraq revealed — under-protected against roadside bombs. The weight of armor required to stop those threats means at least some designs for GCV are over 80 tons, according to a recent Congressional Budget Office study. That would be heavier than any ground vehicle ever mass-produced.

“CBO is just wrong,” one Army source told Breaking Defense. “Both contractors are below [the CBO figures].Their assertion for weight is not based on what the vendors have actually provided to date.” Instead, Army sources said, CBO’s figures appear to derive from early designs long since slimmed down. Even so, however, those confidential sources still talk about numbers north of 50 tons.

Scales himself says that’s still too heavy, either for rapid deployment overseas or rapid maneuver on arrival. He would recommend at most a 45- to 50-ton vehicle — still more heavily armored than the current Bradley — which would rely not on sheer weight of metal but on tactics and technology. The best way to avoid roadside bombs is by going off road, he said, so the enemy does not have any obvious choke-points to mine. The best way to defeat anti-tank rockets, Scales went on, is to shoot them down with a kind of portable missile defense called an Active Protection System, a version of which the Israelis have mounted on their vehicles.

The CBO study, though, says active protection systems are not ready for prime time. Krepinevich, for his part, argues the Army needs to hold off major ground vehicle investments until the invention of much lighter forms of armor.

Congress is reserving judgment. Legislators have funded most of the Army’s requests for GCV, except when they adjusted for a contract dispute that delayed spending on the program. But they’ve also expressed anxiety about GCV’s cost and weight.

That said, the CBO study’s figures for GCV don’t shock Congress: “It kind of confirms what we suspected,” one staffer told Breaking Defense. For now, the Hill is waiting on the Army to complete its study of off-the-shelf US and foreign vehicles. That study, the staffer explained, is part of a “dynamic Analysis of Alternatives update” imposed on the Army by then-Under Secretary for Acquisition Ashton Carter after the service “totally screwed up its original AOA last year.”

“There’s a tremendous amount of support and acknowledgement that the Army needs something,” the staffer went on, “but is that an upgraded existing vehicle or a new ground-up vehicle? That’s still TBD [to be determined]. There are many that don’t think they can afford a new ground-up vehicle.”

Above and beyond the skepticism over the GCV itself, however, the very idea that the heavy brigades are central is coming under increasing attack, for reasons both strategic and fiscal.

Under the current 2013-2017 budget plan, the Army is already set to shrink from its 570,000-soldier peak to 490,000 — a target still above its pre-9/11 strength of 480,000 and likely to fall further as part of any budget deal to head off sequestration. Budgetarily, though, not all soldiers are equal. Pay and benefits are increasingly expensive for military personnel across the board, but the most costly troops are the most heavily equipped.

So in the Army, you save the most by cutting units with lots of helicopters, followed by units with lots of armored ground vehicles. Helicopters have proven critical everywhere from Afghanistan to post-hurricane relief, so the Army’s actually adding more aviation brigades. By contrast, when it announced it would disband eight brigades, the Army left six unspecified and named only two — both armored units.

The Army Chief of Staff himself, Gen. Ray Odierno, told reporters after a recent speech that “we’ll probably see a reduction in the number of heavy units… some small reduction.” In his public remarks at the Center for Strategic and International Studies, Odierno went out of his way to emphasize what are traditionally seen as the service’s secondary, supporting functions, like advisors, logistics, communications, and missile defense, instead of its combat brigades.

That jibes with Krepinevich’s recommendations — up to a point. For example, when reporters asked Odierno after a speech last week whether he could preserve some armored brigades by moving them from the active-duty Army to the National Guard, he cautioned against the idea, which has been bruited by Krepinevich among others. It takes extensive practice to maintain the technically and tactically complex skills of mechanized warfare, Odierno said, and unlike engineering or military police work, those skills are not ones Guard soldiers can practice in their civilian jobs.

“The most difficult formation to sustain over time is a heavy unit,” Odierno said. “It takes more time to maintain it. It takes more time to train it and integrate it, so in my mind I’m not sure it quite fits in the National Guard, because of time constraints that they have.”

Nor has the Chief of Staff meekly accepted AirSea Battle and a future dominated by the Air Force and Navy. In his speech last week, Odierno proposed an “Office of Strategic Landpower” to bring together strategists from the Army, Marine Corps, and Special Operations Command. This is clearly Odierno’s baby, considering that Marine Corps Commandant Gen. James Amos confessed not to having heard of the idea.

“It’s actually NOT about competing with airsea battle or a counter to the AirSea Battle Office” led by the Air Force and Navy, an Army official insisted to Breaking Defense.

“It’s pretty transparently just a competition with AirSea Battle,” one congressional source said, laughing out loud. “Why else would they have it?”

It’ll be up to Odierno’s new office to justify both the Army’s overall strength and its traditional armored core in an era of ever-sharper cuts.

Updated 10:55 am.