The bomb exploded like a dusty thunderclap directly underneath the front left tire of the U.S. Army MaxxPro truck, sending the tall, roughly 20-ton vehicle lurching at least 10 feet forward and scattering chunks of the outer hull like amputated body parts.

It was March 19, 2011, in the Pakhab-e-Shana in eastern Afghanistan’s breadbasket Logar Province. The bomb, later estimated at 250 pounds, had targeted a convoy belonging to the Army’s 10th Mountain Division carrying humanitarian aid to the impoverished village.

What happened next was either the direct consequence of the MaxxPro’s special design, or the expected result of a bomb striking any U.S. military armored vehicle. That distinction lies at the heart of a months-long debate that could shape the direction of American vehicle development.

Inside the more-than-$1-million MaxxPro was a scene of bloody devastation. Of the seven occupants, including five soldiers, an Afghan interpreter and this journalist, two were badly hurt and unconscious; three more were battered, bleeding and groaning but awake, having suffered a mix of concussions, lacerations and broken bones.

But all seven survived. And many of them — myself included — knew without a doubt why: the MaxxPro, a variant of the Pentagon’s Mine-Resistant Ambush-Protected family of armored vehicles, had absorbed or deflected most of the bomb’s force with its sophisticated, and classified, armor blend and force-deflecting, angled underbody.

That truck saved our lives. And we aren’t alone. As a result of the MRAPs’ belated introduction five years ago, “thousands and thousands of lives have been saved and multiples of that in terms of limbs,” then-Defense Secretary Robert Gates said last year.

On Monday Vice Pres. Joe Biden and Deputy Secretary of Defense Ashton Carter headlined a ceremony at the Pentagon honoring MRAP workers and managers. Carter told USA Today that troops riding in MRAPs are 14 times more likely to survive an explosion than those riding in Humvees. The vehicles are credited with saving countless lives,” the Pentagon boasted.

Despite these claims and the powerful anecdotal evidence of the MRAP’s lifesaving qualities, two experts argue that the heavy, expensive vehicles are no more effective than a flat-bottomed, up-armored High-Mobility Multipurpose Wheeled Vehicle, or Humvee, weighing less than half as much and costing just a few hundred thousand dollars.

Humvee vs. MRAP

“MRAPs did not generate large reductions in fatalities beyond those achieved by the factory-armored Humvees and were not cost-effective for any unit,” Chris Rolfe and Ryan Sullivan wrote in Foreign Affairs in April.

Sullivan and Rolfe are economics professors at the Naval Postgraduate School and Syracuse University, respectively. The authors based their article on an academic report they produced for the Naval Postgraduate School, drawing on classified Pentagon data obtained through formal channels. They stressed that the views expressed in the NPS report and the Foreign Affairs article are theirs alone and do not reflect the U.S. government’s official position.

But one of the men most directly responsible for convincing a reluctant military to field MRAPs says Sullivan and Rolfe are wrong. Franz Gayl, a civilian scientist working for the Marine Corps, lobbied his service to purchase blast-resistant trucks as early as 2006 but was initially rejected. Later Gayl publicly criticized the Marines’ acquisitions systems and sought whistleblower protection after senior officials retaliated.

In correspondence with Breaking Defense, Gayl affirms my own belief and calls Rolfe and Sullivan’s analysis “incomprehensible.” “The analysis selectively employs limited sets of unclassified data scrubbed of both granularity and operational context.”

Put another way, “for every four to five soldiers killed while riding in armored HMMWVs that were attacked by IEDs in [Iraq], only one was killed in MRAPs attacked by similar IEDs,” Gayl says, citing figures from the Defense Department Inspector General.

The argument is not academic. Lives, lots of money and the future plans of the Army and Marines are at stake. Since 2007, the Pentagon has spent no less than $45 billion purchasing nearly 27,000 MRAPs to protect against IEDs like the one that could have killed me and those soldiers in Pakhab-e-Shana. As of last year an estimated 1,400 IEDs per month were found by, or struck, U.S. and allied forces — more often than not while they were riding in MRAPs.

With the Iraq war over and the conflict in Afghanistan slowly winding down for the U.S., the Pentagon has begun mulling the fate of its existing MRAPs, while at the same time planning a dramatic expansion of a blast-resistance vehicle fleet, in the form of 55,000 smaller, lighter Joint Light Tactical Vehicles costing an estimated $15 billion in coming years.

“At a time when the Joint Light Tactical Vehicle program works diligently to synthesize the best qualities of both vehicle types [Humvees and MRAPs] in a free and open competition, shedding new light on the authors’ report and resulting articles may be helpful,” Gayl says.

If the MRAPs aren’t worth it, the JLTVs might not be either — and the Pentagon will have to reconsider its pricey approach to protecting soldiers, and embedded journalists, on bomb-strewn battlefields.

Crunching the numbers

Sullivan and Rolfe analyzed what they described as “casualties, vehicle holdings and usage and troop characteristics for an unbalanced monthly panel of about 20-percent of U.S. Army battalions in Iraq from May 2004 through March 2010.”

They concluded that the “data from the battlefield does not support the claims that MRAPs are highly effective in decreasing the number of U.S. casualties.”

Instead, any reduction in combat deaths in units that gained the new blast-resistant trucks actually occurred because the scale and intensity of the fighting decreased, Sullivan and Rolfe claimed. By their reckoning, the drop in death rates has been falsely attributed to MRAPs.

Moreover, the new armored trucks are “bulky and lack maneuverability,” with a commensurate drag on U.S. forces’ combat effectiveness, the authors pointed out. “For most units, tactical wheeled vehicles with medium amounts of protection are just as effective as heavily armored vehicles at reducing casualties. And they are a fraction of the cost,” Rolfe and Sullivan concluded.

They advised only a few units — those engaged in the heaviest fighting — be equipped with MRAPs and similar vehicle.

In his rebuttal, Gayl takes the economists to task first for their limited data sample. “They used this narrow data set to pass judgment on a warfighter-praised and award-winning DoD joint program that has benefited all four services, in both Iraq and Afghanistan,” Gayl says. “This selective exclusion is a defining flaw of the analysis.”

Gayl calls “baseless” the authors’ assertion that a Humvee can reliably protect an occupant as well as an MRAP can. “The analysis did not consider DoD technical evidence that commercially available MRAPs were known to offer significantly superior protection against IEDs than the factory-armored HMMWV.”

Gays says Rolfe and Sullivan failed to carefully examine data on combat casualties in order to understand how troops were killed or wounded and whether they would have been more or less likely to become casualties with the specific types of protection an MRAP provides that a Humvee doesn’t. “There is no evidence that the authors understood this tactical reality,” Gayl says.

Gayl also slams Sullivan and Rolfe for failing to appreciate the ways MRAPs alter battlefield conditions in ways that help drive down U.S. casualties before any direct attack on an American vehicle. “MRAP protection forced changes in insurgent tactics resulting in: 1) fewer attacks, 2) more rapid depletion of insurgent IED caches, 3) increased insurgent attack preparation signatures and 4) increased insurgent vulnerabilities,” Gayl says.

In short, Rolfe and Sullivan are wrong, Gayl insists — MRAPs do save lives.

The maintenance caveat

But the economists are clearly right about a couple things: MRAPs are bulky and expensive. Their sophisticated shaping and armor protection — the main drivers of the armored trucks’ size, weight and $1-million unit cost — proved to be a logistical nightmare for U.S. military units that received the vehicles quickly and without a lot of advance preparation, often in the middle of a deployment.

“Operating, maintaining and sustaining the MRAP has many problems,” Army Maj. Rodney Lipscomb wrote in Army Sustainment magazine.

For one, shipping the MRAPs to deployed units by combined sea and land routes proved slow and, considering the rise in attacks on U.S. supply convoys passing through Pakistan, risky. The Pentagon transported many MRAPs by air at a cost of more than $100,000 per vehicle — an order of magnitude more expensive than sea and ground shipping. Air transport was not without its headaches. Squeezing a 20-ton MRAP into a chartered 747 and unloading it at its destination required a dozen or more workers laboring for hours, as I witnessed firsthand in Afghanistan.

Once in theater, the MRAPs were maintained by military mechanics with little practical experience on the new trucks and few spare parts. At the U.S.-run Bagram Air Field in Afghanistan in 2010, Staff Sgt. Daron Collins told me he and other Army mechanics were replacing an oil pan on a brand-new MRAP when a special nut securing the pan fell off — and disappeared. There were no spare nuts. Procuring a replacement took weeks, during which the potentially lifesaving armored truck was sidelined.

It’s not hard to attack MRAPs on logistical grounds. It’s more difficult to criticize the vehicles for their protective qualities, according to Gayl — and to me and other survivors of militant ambushes.

But Rolfe and Sullivan’s analysis, however flawed, at least has “stimulated a high level debate in the press that will not subside soon,” Gayl says. That debate may influence the Marine and Army decisions about JLTV and other initiatives as the Afghanistan war winds down.