United States President Barack Obama has signed a law that will, for the first time, allow gay and lesbian members of the US armed forces to be open about their sexuality without risking dismissal.
Mr Obama said the change will strengthen the military and is the right thing to do.
He said valour is no more limited by sexuality than it is by creed or colour.
The previous policy, known as "Don't Ask, Don't Tell", allowed gays and lesbians to serve in the armed forces only if they kept their sexuality secret.
That policy led to the discharge of an estimated 14,000 military personnel.
Mr Obama says he hopes some will now be persuaded to re-enlist.
The "Don't Ask, Don't Tell" policy will officially continue until such time as the Defence Secretary and Congress certify that the military is ready and it is deemed not to impact combat effectiveness.