What will the Pentagon do with about 6,000 excess MRAPs (Mine Resistant Ambush Protected vehicles) after the major Army and Marine Corps combat elements leave Afghanistan at the end of 2014? The MRAPs are worth more than $4 billion.

Perhaps just as important is where will the Army and Marines get the funds to operate, maintain and replace the roughly 20,000 they have tentatively decided to keep as standard equipment?

MRAPs are the family of heavily armored vehicles with unique

V-shaped hulls that were rapidly designed and produced beginning in 2006 to protect against improvised explosive devices, or IEDs, which have been the main cause of deaths and injuries to U.S. and coalition troops in Iraq and Afghanistan.

In Afghanistan from 2009 to 2010, the predecessor personnel carrier, the HMMWV, or Humvee, had an occupancy death rate of 80 percent when hit by IEDs, according to a January 2011 report by the Congressional Research Service (CRS). The MRAP’s fatality rate during the same period was 15 percent, a result that may have saved dozens of lives a month, the CRS said.

In the process of rushing these vehicles to the battlefield, the Pentagon used five manufacturers and created 25 versions that fit into three categories — those for urban combat that can carry seven soldiers; those for security, convoy escort or ambulance duty that can take up to 11 people; and those used to clear mines or IEDs that could handle 13 people.

When the main fighting switched to Afghanistan, about 8,000 of a newer, lighter version called the All Terrain Vehicle (M-ATV) were purchased. They were designed for that country’s more rugged, mountainous areas, according to the CRS report.

Through 2011, the Defense Department bought and fielded more than 27,000 MRAPs, according to the Government Accountability Office, which on March 31 sent Congress a briefing on how the Army and Marines are trying to determine what equipment designed specifically for fighting in Iraq and Afghanistan should be retained and what should be discarded.

MRAPs, in Pentagon jargon, are nonstandard equipment — vehicles that were not found in core Army and Marine units before these wars. The more than $45 billion spent on MRAPs during the past six years came out of Overseas Contingency Operations (OCO) accounts, which are supplementary funds appropriated by Congress to support war-fighting. The funding didn’t come from the services’ core budgets.

The cost of individual MRAPs has varied, but an average of

$1.54 million a copy has been used in Pentagon budget documents. That figure includes anywhere from $500,000 to $1 million for the base vehicle, with hundreds of thousands more added for computerized electronics, monitors, jammers, radios, additional armor and other elements, according to congressional sources.

The MRAPs that the Army and Marine Corps decide to keep will have to be paid for out of their core budgets, which are already under pressure. Meanwhile, they are requesting OCO funds in fiscal 2013 to support their MRAP programs, according to the GAO.

For example, the Army is seeking more than $900 million in OCO funds to repair and upgrade the vehicles. An additional $40 million would be used to store MRAPs as war reserves, pre-positioned in holding areas, according to budget material sent to Congress.

The Army plans to keep about 18,000 MRAPs, according to the GAO. The Marine Corps has tentatively decided to keep 800 MRAPs and 300 M-ATVs, according to congressional sources.

How to handle nonstandard equipment is an issue bigger than MRAPs, however.

For example, as part of its post-Iraq-Afghanistan transition work, the Army since 2004 has reviewed 409 equipment systems, according to the GAO. Of those, only 11 percent have been determined useful for the future, including MRAPs. Thirty-seven percent of the systems under review have been deemed “not needed and should be terminated,” according to the GAO. The remaining 52 percent, on which the Army has made no decision, are nonstandard equipment being used in Afghanistan and other overseas operations and paid for with OCO money.

The Marine Corps generally funds its nonstandard equipment through its Urgent Needs Process and, after two years, makes a decision on continued funding. Since 2008, the Marines have decided that 63 percent of 144 unique capabilities supplied to commanders under the program would be needed in the future. Seventeen percent would not be needed, and 20 percent need further evaluation.

Other nonstandard equipment purchased rapidly under special procurement programs developed for Iraq and Afghanistan includes advanced gunsights; equipment for gunshot detection, special surveillance and construction; and specialized radios and flat-screen televisions. A September 2011 GAO report said that in Iraq, as of March 2011, the Army had about $4 billion in such equipment.

Among the nonstandard items is a category the Army refers to as “White” equipment — gear that was contractor-purchased but government-owned. This primarily involves items such as “fire trucks and ambulances as well as equipment used for laundry and food service, construction, power generation and distribution and transportation,” according to a 2010 Army directive. In Iraq, as of March 2011, White equipment represented about $2.5 billion, or 36.5 percent, of all Army equipment remaining in-country.

A long-standing program allows U.S. state and local governments to seek surplus White equipment. They are required to pay only transportation expenses. But those costs are discouraging when the surplus equipment is in Iraq, Afghanistan or Kuwait. The GAO’s 2011 report noted that only $6 million worth of such items had been distributed to such entities as of April 2011.

Most public talk about defense matters is focused on the spending for new weapons for the next war. But in these belt-tightening times, it is worth thinking about what happens to the billions of dollars of equipment already used.

For previous Fine Print columns, go to washingtonpost.com/fedpage.