Marine Commandant Gen. James Amos laid out his concerns saying, "Commanding officers never delegate responsibility. They should never be forced to delegate their authority."
Gen. Mark A. Welsh III, from the Air Force, labeled sexual assault in the military a "cancer " and said that "none of us will be standing still" in trying to end it. However, Welsh added, "Commanders shouldn't just be part of the solution. They must be part of the solution or there will be no solution."
In his opening statement committee chairman Sen. Carl Levin, D-Mich., and the committee chairman, said, "The problem of sexual assault is of such scope and magnitude that it has become a stain on our military." He added that real progress would not be seen without a cultural change in the military from the top down."
Sen. James Inhofe (R-Okla.), the ranking Republican on the committee, opposes Gillibrand's bill, saying, "No change is possible without commanders as agents of that change."
On Tuesday, Gillibrand told the panel of military officers, "You have lost the trust of the men and women who rely on you." She added that the biggest challenge is that sexual assault victims are wary of stepping forward because they are "afraid to report, they fear their careers are over – they feel they are being blamed ."
Last month the Pentagon's most recent report on sexual assault in the military estimated that as many as 26,000 military members may have been sexually assaulted last year, up from an estimated 19,000 assaults in 2010.
Sen. Claire McCaskill (D-Mo.) said that number was confusing because it describes incidents of "unwanted sexual contact" which includes sexual harassment, an unwelcome work environment, touching and rape.
Sen. John McCain (R-Ariz.) a strong military supporter and former Naval officer who was held as a prisoner of war during the Vietnam War, said he is concerned how sexual assault could affect recruitment and retention in the military.
"Last night a woman came to me and said her daughter wanted to join the military and could I give my unqualified support for her doing so," said McCain. "I could not."
"I cannot overstate my disgust and disappointment over the continued reports of sexual misconduct in our military," he said. "We've been talking about the issue for years and talk is insufficient."