WASHINGTON — Shocked and offended by explicit questions, some U.S. servicemen and women are complaining about a new sexual-assault survey that hundreds of thousands have been asked to complete.

The survey is conducted every two years. But this year’s version, developed by the Rand Corp., is unusually detailed, including graphically personal questions on sexual acts.

Some military members say they were surprised and upset by the questions, and some even said they felt re-victimized by the blunt language. None of them would speak publicly by name, but Pentagon officials confirmed they had received complaints that the questions were “intrusive” and “invasive.”

The Defense Department said it made the survey much more explicit and detailed this year in order to get more accurate results as the military struggles to reduce its sexual assaults while also encouraging victims to come forward to get help.

The survey questions ask about any unwanted sexual experiences or contact, and include specific wording about men’s and women’s body parts or other objects, and kinds of contact or penetration.

“We’ve had a number of complaints,” said Jill Loftus, director of the Navy’s sexual assault prevention program. “I’ve heard second- and third-hand that there are a number of women, officers and enlisted, who have gotten to the point where they’ve read the questions and they’ve stopped taking the survey. They found them to be either offensive or too intrusive – ‘intrusive, invasive’ – those are the words they used.”

About 560,000 active duty, National Guard and Reserve members were invited to fill out the questionnaire – about five times the number the survey was sent to two years ago. Officials will not say how many responses they have received so far.

Early last year, a report on the 2012 anonymous survey results set off a furor when it estimated that 26,000 military members may have been sexually assaulted or subjected to unwanted sexual contact.

Exasperated members of Congress complained that the Defense Department wasn’t doing enough to combat sexual assault and tried to force changes in the Pentagon’s legal and command procedures.

Some major changes were enacted, such as stripping commanders of the ability to overturn verdicts and strengthening protections for victims. But other potential changes – such as keeping defendants’ commanders completely out of the process – are still not law.

Sen. Kirsten Gillibrand, D-N.Y., who has pressured the military to deal with its sexual assault problem, said changing the survey questions could skew the study over time.

“I am concerned the new survey was done in a manner that not only prevents comparing apples to apples from previous years.… I hope this isn’t a case of, ‘If you don’t like the answer, change the question.’ ”

In addition to the Rand questions, Loftus said the Navy sends its own survey to sailors and Marines that doesn’t get as specific.

But Rand analysts say the more detailed questions are necessary. So does Nate Galbreath, the senior executive adviser for the Pentagon’s sexual-assault prevention office.

“This is a crime of a very graphic nature,” Galbreath said. “For us to improve our understanding, it sometimes requires asking tough questions.”

Kristie Gore, one of the project leaders at Rand, said participants were told they could skip questions they found upsetting, or simply not take the survey. In the end, she said, Rand received a “relatively small” number of complaints.

Andrew Morral, the other project leader, said the questions were based on the Uniform Code of Military Justice.

“If you don’t use precise language to describe different types of sexual assault and harassment, people define those terms for themselves in different ways, which leads to ambiguous results,” he said.

The report on the 2012 survey, which was released early last year, showed sexual assault incidents rose from about 19,000 in the 2010 survey to 26,000.