In the US, more than 13,000 American service members have been discharged under DADT, which was implemented in 1993.
The ban continues despite numerous studies over the past two decades that have shown no negative impact from allowing gays and lesbians to openly serve in the military.
According to a February report (pdf download) from the Palm Center at the University of California, Santa Barbara, allowing homosexuals to serve contributes to improving the command climate in foreign militaries, decreasing harassment, retaining critical personnel, and enhancing respect for privacy.
US military leaders say they're aware of precedent in other countries. Adm. Mike Mullen, during a Congressional hearing on Feb. 2, 2010, said he had spoken to his counterparts in countries that lifted the bans and they told him there had been “no impact on military effectiveness” as a result, and that he was aware of no studies showing that ending DADT would harm unit cohesion.
Already, US service members serve alongside gays and lesbians. The Williams Institute at the University of California, Los Angeles, has estimated that some 66,000 gay and lesbian troops serve (pdf download) in the US forces today. And Britain, a key ally in Iraq and Afghanistan, has allowed homosexuals to openly serve in its military for a decade.