The number of private contractors working for the U.S. Defense Department in Iraq grew eight-fold over the past year, a rate that far outpaces the growing number of American troops training and advising Iraqi soldiers battling Islamic State militants.

The sharp increase, disclosed in a recent Pentagon report to Congress, underscores the military’s reliance on civilians even for missions with relatively small troop presence.

“If you look at the size and the composition of the forces that have been deployed in support of Operation Inherent Resolve, that’s changed markedly in the past year,” said Rick Brennan, a senior political scientist at the RAND Corp. and a retired Army officer.

As of January, 2,028 contractors were in Iraq, up from just 250 one year earlier, according to the Pentagon’s data. There are roughly 3,700 American troops there now, compared to 2,300 in January 2015.

That number of military contractors represents just a fraction of the contractors employed by the U.S. in Iraq. In addition to the 2,028 Pentagon contractors, another 5,800 are employed by other agencies, including the State Department.

In the 1980s, the U.S. military decided to hire contractors to work in support roles that had historically been done by troops. That includes jobs like food services, maintaining housing units, water purification and “all those those other things that go with maintaining troops in the field for a long time,” Brennan said. The plus-up in Iraq is likely for contractors in those types of roles.

“What’s occurred then is as you deploy more forces to theater, you have to provide increased total number of contractors,” Brennan said.

During the Iraq War, there was a little bit more than one-to-one ratio of contractors to soldiers, he said. Now in Iraq, more than 30 percent (618) of the contractors are working in maintenance and logistics jobs. Nearly 20 percent (381) are translators and 13 percent (263) are in base support positions, according to the data. Contractors are also working in security, transportation, construction, communication support, training, management and administrative roles.