Military leaders and members of the Senate Armed Services Committee debated how commanders should be involved in combatting sexual assault at a hearing Tuesday. (Sarah Parnass/The Washington Post)

The uniformed chiefs of the Army, Navy, Air Force, Marine Corps and Coast Guard, flanked by dozens of junior officers, jammed into a Senate hearing room Tuesday to field hours of uncomfortable, sometimes withering questions from lawmakers about an epidemic of sexual assaults.

Senators from both parties made clear they are fed up with years of sex-crime scandals despite repeated declarations from military leaders of “zero tolerance” for sexual abuse. Drawing a wide arc from the Navy’s Tailhook disaster in 1991, when aviators assaulted 90 people during a convention gone wild, to more recent embarrassments such as last month’s arrest of the Air Force’s top sexual-assault prevention officer on charges of sexual battery, legislators pressed all the brass arrayed before them to finally crack down.

“What’s different this time? What’s different this time, if we have a history of this repeating itself and nothing ever being done?” demanded Sen. Joe Manchin (D-W.Va.). “It’s almost intolerable that we can continue on this current path.”

The military chiefs acknowledged that they had neglected the spread of sexual abuse in the ranks. They said they were amenable to legislative changes that would take tougher action against sex offenders and provide more support to victims.

But they drew the line at one bill, co-sponsored by a fifth of the Senate, that would strip commanders of the legal power to oversee major criminal cases and transfer that authority to uniformed prosecutors. Such a change, they argued, would undermine the foundation of military culture by questioning the judgment of unit commanders.

Sen. Claire McCaskill, D-Mo., grew heated in questioning military leaders during a Senate Armed Services Committee hearing Tuesday. (Sarah Parnass/The Washington Post)

“Without equivocation, I believe maintaining the central role of the commander in our military justice system is absolutely critical,” said Gen. Ray Odierno, the Army’s chief of staff. “Removing commanders, making commanders less responsible, less accountable, will not work. It will hamper the delivery of justice to the people we most want to help.”

The chiefs did not play down the severity or scope of sex crimes in the armed forces and promised to redouble their efforts to root out abuse. And they acknowledged that they had not always done enough in the past.

Army Gen. Martin E. Dempsey, the chairman of the Joint Chiefs of Staff, cited the demands and distractions of 12 years of war, saying that he had not always monitored subordinate commanders closely enough to ensure that they took sexual abuse seriously enough.

“I’ll speak for myself: I took my eye off the ball a bit in the commands I had,” Dempsey said. “When you tie it all together, I wouldn’t say that we’ve been inactive, but we’ve been less active than we probably need to be.”

The influence of gender was a palpable factor during the hearing. The six male military chiefs received some of their toughest grilling from the seven women on the Senate Armed Services Committee.

“You have lost the trust of the men and women who rely on you that you will actually bring justice in these cases,” said Sen. Kirsten Gillibrand (D-N.Y.), the lead sponsor of the bill that would strip commanders of their legal authority over serious crimes.

She asserted that raw sexism and ignorance were a large part of the problem. “Not every single commander necessarily wants women in the force,” she said. “Not every single commander can distinguish between a slap on the ass and a rape because they merge all of these crimes together.”

Sen. Claire McCaskill (D-Mo.), a former district attorney, didn’t hesitate to chide Odierno, a hulking combat veteran, for his statement that the military cannot “simply prosecute our way out of this problem.”

“With all due respect, General Odierno, we can prosecute our way out of . . . the problem of sexual predators, who are not committing crimes of lust,” she said. “My years of experience in this area tell me they are committing crimes of domination and violence. This isn’t about sex. This is about assaultive domination and violence.”

Some male lawmakers, however, suggested that the increased integration of women into the armed forces was a factor.

“If we’re going to have women in combat, I think the potential for the issue to increase is going to become even greater,” said Sen. Saxby Chambliss (R-Ga.). Noting that most enlisted troops are between 17 and 23 years old, he added, “Gee whiz, the hormone level created by nature sets in place the possibility for these types of things to occur.”

Last month, the Pentagon released a report estimating that the number of military personnel victimized by sexual assault and related crimes had surged by about 35 percent over the past two years.

The Pentagon survey estimated that 26,000 troops experienced “unwanted sexual contact” last year. Yet only a fraction of that number — 3,374 — filed sexual-assault reports with military police or prosecutors. Defense officials said most victims are reluctant to press charges because they fear retaliation or ostracism from their units.

The military chiefs said it was the responsibility of commanders to ensure that victims trust their leaders and the military justice system to investigate and prosecute sex crimes properly. They promised that commanders would be held strictly accountable for any failure to do so.

The chiefs, however, were hard-pressed to name any specific cases when Sen. Jack Reed (D-R.I.) asked whether any commanders had been fired for tolerating sexual assaults in their units.

Odierno said several Army commanders had been relieved for “toxic leadership” in general, including a tolerance of sexual harassment or abuse. The commandant of the Coast Guard, Adm. Robert J. Papp Jr., said one officer was fired two years ago for failing to report a sexual assault that had been brought to his attention.

The leaders of the Navy, Air Force and Marine Corps could not cite any such instances at first. Later in the hearing, after aides whispered in their ears, the leaders of the Air Force and Marines corrected themselves to say that a handful of officers had in fact been relieved or disciplined for that reason.

Ed O’Keefe and Rachel Weiner contributed to this report.