But high dropout rates at some of these colleges, difficulty in transferring credits, higher tuition bills than at public colleges and skepticism from some employers about the value of the degrees are all creating unease among some in Congress.

“For-profit schools see our active-duty military and veterans as a cash cow, an untapped profit resource,” said Senator Tom Harkin, Democrat of Iowa, the chairman of the Senate committee that oversees federal education policy. “It is both a rip off of the taxpayer and a slap in the face to the people who have risked their lives for our country.”

It is a concern echoed by eight current and former recruiters from some of the nation’s largest for-profit chains, who in interviews said the intense drive to enroll veterans had led them, at times, to sign up military personnel for classes when they were all but certain they would drop out or fail.

“There is such pressure to simply enroll more vets  we knew that most of them would drop out after the first session,” said Jason Deatherage, who worked as military admissions adviser at Colorado Technical University until this spring, when he was fired, he said, for not meeting his quota. “Instead of helping people, too often I felt like we were almost tricking them.”

In interviews, veterans offered conflicting views. Some said the online classes enabled them to complete their studies while also tending to their families, and perhaps a day job. But other veterans said it was a waste.

“I felt like I made a horrible, horrible decision,” said Jason Longmore, 31, a Navy veteran who spent six months at Westwood College, based in Denver, only to conclude that the degree was not attractive enough to employers, forcing him to repeat classes elsewhere before he could transfer credits to a Colorado state university.

Robert L. Songer, a retired Marine colonel who is the lead education adviser at Camp Lejeune in North Carolina, said some of the for-profit colleges hounded active-duty personnel there as they pursued “hot leads,” calling them repeatedly to get a piece of the military tuition grants.