Few were more stunned and saddened by Robin Williams' death than the US servicemen and women he loved to entertain, be it on the frontlines or by their hospital beds.
Williams has taken part in no fewer than six USO entertainment tours since 2002, the military charity said Tuesday, delighting nearly 90,000 troops across 13 countries including Afghanistan and Iraq.
"Robin was a gifted actor and comedian, but he was also a true friend and supporter of our troops," said Defense Secretary Chuck Hagel in a statement.
"From entertaining thousands of service men and women in war zones, to his philanthropy that helped veterans struggling with hidden wounds of war, he was a loyal and compassionate advocate for all who serve this nation in uniform."
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His fondness of Americans in uniform was vividly captured in 2012 when an outdoor show at Camp Arifjan in Kuwait was interrupted by the nightly playing of "Retreat" on the base's sound system.
Up stood the entire audience to solemnly observe the lowering of the US flag. Williams, sporting a ski hat, likewise snapped to attention -- and then, when it was over, he expertly riffed off the moment.
"That's pretty weird, in the middle of your act, having everybody go 'ouph!'," quipped the veteran stand-up comic, spinning 180 degrees on his heels. "It's like in the middle of sex, going: 'bye-bye!'."
"That was after we'd flown all night to Qatar and to Kuwait, hadn't seen a hotel, really hadn't had a chance to clean up," recalled USO senior vice president John Hanson, who accompanied Williams on that tour.
"Everybody was whipped. But his good nature was something to watch," Hanson told AFP in a telephone interview.
Stateside, Williams volunteered for visits to wounded soldiers at the Walter Reed military hospital in Washington. He also shared the bill at a star-studded 2012 Stand Up for Heros gala for disabled veterans in New York.
Humor, he explained backstage at the benefit gig, could be a potent form of therapy for wounded warriors, "part of coming back, of coming home."
"These guys are incredible -- guys and girls," he added. "This is just something that really humbles me, to be in their presence. It kind of makes me go, 'Wow'."
In a way, by performing live before an audience real soldiers, Williams was reprising one of his most memorable characters -- the irreverent US armed forces radio DJ Adrian Cronauer in the 1987 movie "Good Morning, Vietnam."
The real Cronauer, 75, who lives in southern Virginia, told Washington's WTOP that director Barry Levinson didn't want Williams to meet him before the film's premiere, fearful that it might alter his manic performance.
"That was all Robin Williams. All Robin Williams," he said. "I'm a much more laid back person."
Following in the footsteps of Bob Hope, whose morale-lifting USO shows during the Vietnam War became the stuff of comedy legend, Williams was among the first USO entertainers to visit American troops in Southwest Asia.
From the 2007 tour, Hanson remembered how Williams -- barely able to speak after a blowing out his voice during an Iraq show -- reluctantly accepted the gift of a St. Christopher medal from a soldier collecting body armor prior to the tour's departure from Camp Phoenix outside Kabul.
"Robin took it, turned it over in his hands, just studying it," Hanson told AFP in a telephone interview.
"And Robin said, 'Wait, you gave me yours, I'll give you mine,' and he unbuttoned his shirt and pulled out a large cross," he said.
"And so they exchanged these bits of protection and each of them felt more powerful than body armor."
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