Experts on the nonpartisan commission, made up of active duty and retired military service members, warned the loss of women from the ranks because of limited advancement opportunities could hurt the force overall.
"The performance of the nation's military is tied to the individual's belief that he or she will be recognized regardless of his or her background," the commission wrote in its draft report.
There are more than 213,000 women on active duty in the U.S. military, comprising 14 percent of the overall force and serving in each of the service branches, according to Women in Military Service for America. But disproportionately small numbers are flag officers or generals.
Women are least represented in the Marine Corps, which is 93 percent male. Only 3 percent of the Marines' flag officers and generals are women.
Opponents of change say close-combat conditions are no place for women, who don't have the physical strength to survive and whose presence would bring sexual tension to the ranks.
"We're talking about ground combat, nose-to-nose with the bad guys, living in the mud, eating what's on your back, no hygiene, and no TV," retired Marine Lt. Gen. Frank Petersen, a member of the commission, said during a meeting in September.
"How many of you have seen how infantrymen, the ground troopers, live, and how many of you would volunteer to live like that?" he asked a panel of female military service members and veterans.
Elaine Donnelly of the Center for Military Readiness, which opposes a change, said she doesn't doubt the courage of female service members, but warns that changing the policy puts the entire force at risk.
"Women do not have an equal opportunity to survive or to help fellow soldiers survive," Donnelly said. "The demands of close combat are such that women cannot physically compete or survive like men."
Donnelly also warned that lifting the ban on women in close combat units could force a reassessment of the Selective Service system, which in turn could require all American women to register for the draft and potentially be called into service at time of war.
Former Marine Corps Commandant Gen. James Conway said last year he believes many women know they are not fit to serve in certain roles and don't want to.
"There are certain demands of officers in a combat arms environment that our women see, recognize, appreciate, and say, 'I couldn't do that -- in fact, I don't want to do that because I don't think it best prepares me for success if I am trying to do those things against the male population at lieutenant, captain, major, and lieutenant colonel,'" Conway said at a commission meeting.
But several studies show women not only want to assume roles in close-combat units, they are well qualified to do so.
"There is a lack of empirical data on female fitness and correlation with battle performance other than basic physical requirements by the Services," researchers wrote in a white paper prepared for the commission.
A study by the RAND Corporation in 1997 also dismissed claims that unit cohesion and morale would be adversely affected by allowing women in combat units.
"Any divisions caused by gender were minimal or invisible in units with high cohesion," RAND researchers wrote well before 9/11 and the influx of women serving alongside men in Iraq and Afghanistan. "The presence of women was also cited as raising the level of professional standards."
Asst. Secretary of Veterans Affairs Tammy Duckworth, who lost both legs and severely damaged her arm in a helicopter attack in Iraq, told the commission last year that she has been in the trenches and has proven women can succeed.
"I've lived like that," she said. "I have lived out there with the guys in the FOB [forward-operating bases] and I would do it. I would do it in a minute for the honor of being able to serve next to some of the greatest folks that I've ever been able to serve next to.
"It's about the job. Women are doing that right now," she added.