The Supreme Court announced last week that it would not review a lawsuit challenging the military's 'don't ask, don't tell' policy forbidding homosexuals from serving openly. The Obama administration had asked the court not to take the case as the president considers ending the ban. News that the president would change the policy had inspired a group of retired flag officers to argue on this spring that service by openly gay individuals would harm morale, discipline, cohesion, recruitment and retention in the U.S. military. They wrote as part of a larger effort by more than 1,000 retired officers to keep the ban in place. According to the generals and admirals, allowing gay men and lesbians to serve openly would make parents less willing to allow their sons and daughters to enlist. The argument assumes that anti-gay sentiment is so fierce and widespread that moving to a policy of equal treatment would drive away thousands and could ultimately 'break the All-Volunteer Force.' Not only is there no evidence to support these conclusions, but research shows conclusively that openly gay service members would not undermine military readiness. Tradition is a critical military value, and the armed forces have a long-standing tradition of banning gay men and lesbians. Equally important military traditions, however, are learning and adapting -- and my colleagues made claims as if no new knowledge has been acquired over past decades, during which time Israel and Britain joined more than 20 other nations to allow openly gay individuals to serve without overall problems. In Britain and Canada, polls had indicated that thousands would resign if gays were allowed to serve, but when the bans were lifted, almost no one left. The British Defense Ministry conducted several assessments of the policy change and called it a 'solid achievement.' The flag officers neglected to acknowledge Britain's experience, instead dismissing the relevance of nations such as 'Denmark, the Netherlands and Canada.' While it is true that the U.S. armed forces are unique, it is important that we not marginalize the lessons learned in other coun! tries -- particularly those that often conduct joint operations with us. But it is not just foreign militaries that show service by openly gay individuals works. The U.S. military itself has had successful experiences. Enforcement of the ban was suspended without problems during the Persian Gulf War, and there were no reports of angry departures. A majority of U.S. service members say they know or believe that someone in their unit is gay, according to a 2006 Zogby International poll, and most of those who know of openly gay peers report no detriment to morale or cohesion. A recent study co-authored by Laura Miller of Rand Corp. found no correlation between a unit's readiness and whether known gays serve in it. And last year, four retired flag and general officers studied all available evidence and found that allowing gays to serve posed no risk to force readiness. While the proper timing of repealing 'don't ask, don't tell' remains uncertain, it is evident to me that a policy change is inevitable. More than three-quarters of the public favors the change. Polls show that even a majority of Republicans support allowing openly gay people to serve. Within the military, the climate has changed dramatically since 1993. Conversations I've held with service members make clear that, while the military remains a traditional culture, that tradition no longer requires banning open service by gays. There will undoubtedly be some teething pains, but I have no doubt our leadership can handle it. Given the inevitability of change, whether via executive order or legislative repeal, it will be important for senior leaders to send clear signals of support to the rank and file. Every general officer knows that mixed signals undermine leadership. Indeed, studies show that when organizations implement controversial change, signals from the top must be clear. For such a large group of retired senior officers to oppose the inevitable could cause the very disruptions they predict. The officers who oppose lifting the ban argued that there is 'no compelling national security reason' to let openly gay troops serve. They also say, however, that 'losses of even a few thousand sergeants, petty officers and experienced mid-grade officers' -- those they believe might bolt -- are unaffordable. Under current policy, we have lost more than 13,000 of those people, such as the Arabic language speaker featured in the new film 'Ask Not.' In addition, researchers at the University of California at Los Angeles have found that nearly 4,000 people leave voluntarily each year because of the ban, and that more than 40,000 recruits might join if the ban is ended. President Obama has wisely indicated that he will consult carefully with military leadership before making any change to 'don't ask, don't tell.' In the same way that military leaders take into account research about what works and what doesn't when contemplating a new strategy or doctrine, it will be important for the conversation about gays and lesbians in the military to be informed by data, not speculation or emotion. That people on all sides of the issue feel strongly about it is more reason, not less, to let the evidence do the talking. The writer, a retired Army general, was chairman of the Joint Chiefs of Staff from 1993 to 1997. 