A day after a Taliban suicide bomb killed 12 Americans in a NATO convoy in Kabul, the military has yet to release details about the victims, but it appears that eight of them were civilian contractors.

Had all the Americans killed been soldiers, the attack would have resulted in the fourth largest single day loss for American forces in more than a decade of war here.

The death of eight contractors alongside NATO soldiers stands as a sharp reminder of the heavy reliance the US military and NATO forces have placed on private contractors to wage this war.

Throughout the American-led wars in Afghanistan and Iraq, civilians have played a vital role doing everything from running cafeterias and laundry services to training local militaries and operating drones.

With the US reliant on an all-volunteer military, it’s unlikely that the US could have sustained more than a decade of foreign wars without these contractors. However, as contractors have become increasingly involved with combat operations, their role in America’s wars has become ever more controversial.

“Information about this aspect of the war only comes out when something happens or goes wrong, but all in all it’s a very secretive and not transparent part of the war,” says Thomas Ruttig, co-director of the Afghanistan Analysts Network in Kabul. The recent bombing “should be used as an opportunity to discuss their role, and also better define their role so it becomes more transparent what they’re doing over here.”

In Afghanistan, the US Defense Department alone employs nearly as many private contractors as there are US military personnel here. As of March, there were 90,000 private contractors working for the DoD, while there were about 99,000 US service members deployed here, according to the Brookings Afghanistan Index put out by the Washington-based Brookings Institution. This figure does not include private contractors working for other government agencies in Afghanistan.

Although NATO forces have made training the Afghan Army and police one of their major priorities here, they are still reliant on approximately 2,765 private contractors to act as trainers.

While the nature of many of these contractors’ work remains unclear, there is evidence that some may be involved with direct combat operations against the insurgents here. Others support counterinsurgency efforts through training local forces, installing and maintaining surveillance equipment, and supporting intelligence operations.

With so many civilians on the battlefield, determining what makes a combatant or a civilian in Afghanistan has become more ambiguous, especially since NATO forces adopted the counterinsurgency doctrine.

Counterinsurgency strategy relies heavily on reconstruction efforts, such as road building projects. These activities used to be the mainstay of civilian agencies in places like Afghanistan, but now many of these projects are done in the interest of supporting the military’s counterinsurgency goals rather than for entirely humanitarian purposes.

As a result, even private contractors not employed directly by NATO or the Defense Department may find themselves working in support of military goals.

For Afghans, the vast sums foreign forces spend on contracting is a growing point of contention.

“I think that when the Americans have the same number of civilians as they do military forces it’s a waste of money, especially since America is also facing an economic crisis,” says Mahmoud Khan, a member of parliament from Kandahar province. “From the beginning, they needed to send Afghans to foreign countries to give them degrees. If they’d done that there would have been professional Afghan advisers who could have worked here forever.”