LGBT advocates say there are parallels with the integration of African Americans in and women, who were serving in separate regiments.
In 1948, President Harry Truman signed an executive order mandating equal treatment and opportunity. It also made it illegal under military law to make a racist remark.
Women's roles in the Armed Forces were expanded in 1973 after the end of the draft the establishment of all volunteer force.
The Pentagon says implementation of new policies on gays should be an orderly process after a full review.
"These are the same things we heard 17 years ago: It's such a complicated problem, a thorny set of issues, this is rocket science," said Aaron Belkin, director of the Palm Center, an organization dedicated to research on issues of gender, sexuality and the military. "But this is a form of obstructionism."
A 1993 Rand Corporation study concluded that sexual orientation was not "germane" to who can serve and recommended establishing a standard of conduct that is enforced by leaders at every level of the chain of command.
"A single rule applies easily to everyone, there is strong leadership and everything else follows from that," said Belkin.
The study also reviewed militaries in now 26 countries that have already opened doors to gays. Canada, Britain and Australia said initial fears about morale and combat readiness proved to be unfounded.
But Elaine Donnelly, president for the Center for Military Readiness
, which promotes "sound military personnel policies in the armed forces," said the repeal will create chaos.
"No matter where you turn there are going to be problems the military doesn't need," said Donnelly. "The only thing beneficial about [the review], and even the secretary of defense said this, is to figure ways to mitigate the problems. Not once have they pointed to a single benefit for the military."
Her group opposes repeal, saying the 1993 law remains valid. They cite military living conditions with lack of privacy. Allowing gays to live openly presents an "unacceptable risk" to good order, discipline, morale and unit cohesion, which are essential for combat readiness.
Their research concludes separate housing would be impractical and expensive and "unacceptable" to LGBT activists.
Pretending that sexual tension does not matter would create a "hostile work environment, tantamount to forcing women to live in close quarters with men," says its position statement.
They also fear increased sexual misconduct and oppose any mandatory sensitivity training.
Donnelly also said lifting the ban would also put pressure on Congress to repeal the Definition of Marriage Act (DOMA), which defines marriage as only between a man and a woman.
Even the LGBT advocates say DOMA presents a problem for extending health benefits to same-sex partners who were married in states that permit gay marriage and in policies that use the word "spouse."
The Obama administration recently afforded health benefits to same-sex partners serving in the State Department.
Military policies that are less narrowly defined by the word "spouse," such as "family" or "dependents," may be more generous to same sex-couples.
"It's not fair and it's not ideal, but that is the law of the land and it's really not complicated," Donnelly said. A waiver of Congress would be required to override DOMA, say legal experts.