Navy Lt. Gary Ross, right, and Dan Swezy exchange wedding vows in Duxbury, Vt., after midnight, just as “don’t ask, don’t tell” expired. (Toby Talbot — Associated Press)

DADT is dead. Over. Gone.

Almost 18 years after its birth, “don’t ask, don’t tell” passed into the history books as of 12:01 a.m. Tuesday. Gay men and lesbians may now serve openly in the U.S. military; the Defense Department says 2.3 million troops have been provided with training on “what is expected in a post-repeal environment.”

“Don’t ask” was the brainchild of Charles Moskos, a sociology professor at Northwestern University whose proposal won the backing of President Bill Clinton’s administration. Moskos, as it happens, had his own reservations about the policy that he created, but he could think of none better. In an interview, he once compared “don’t ask” to Winston Churchill’s definition of democracy: “It’s the worst system possible, except for any other.”

Moskos died in 2008, but his policy lived on. Last year, in an essay for The Post, the professor’s son wrote that he was convinced his father — more concerned about issues of privacy than of sexual orientation — would have come to have supported the repeal of “don’t ask.”

“Ever the contrarian, my father would have savored the irony (and media attention) of renouncing the law he defended for many years,” Peter Moskos wrote. “Next, he would have flown to a war zone to help the military figure out the best way to have openly gay men and women serve.”

On this morning, on the occasion of the policy’s end, we recommend to you a story by our colleague Ed O’Keefe on gay military personnel and veterans, and what service during “don’t ask” has meant. Over at Federal Eye, check out a piece on a new publication by and for gay and lesbian members of the U.S. military. Its publishers say it will be available for free at about a dozen Army and Air Force bases starting today.