Norwegian doctor Gilbert, who had treated patients during the 1982 Israeli invasion of Beirut and later in Palestinian territories, speaks about his new mission
Bespectacled like Clark Kent but playing like Superman at a sunbathed Rod Laver Arena, world number 58 Chung became the lowest ranked player into the last four at Melbourne Park since Marat Safin in 2004.
Chung later admitted to thinking prematurely about victory and what it might mean for his expectant nation.
"I think (in the) last game, many things come together. If I win one more point, I make history in Korea," he told reporters. "Something I (was) thinking like that. I have to think about the ceremony. Anyway, I had to stay calm because... the match was not finished yet."
Federer, the 19-time Grand Slam champion, who hasn't lost in five matches against Berdych in Melbourne, will play in his 43rd Grand Slam semifinal, a record for the post-1968 Open Era.
The Swiss legend has yet to face Chung, who has got past six-time champion Novak Djokovic and world No.4 Alexander Zverev to get to the last four.
Federer's latest victory was his 92nd in 105 matches in Melbourne to make the Australian Open his most successful Grand Slam in terms of matches won.
"I'm happy I got out of the first set. It ended up being the key of the match," he said.
"I just tried to hang around, tried to play a bit more aggressive, get some rhythm going, because Tomas found that early.
"That's why I was under pressure. It was definitely very close, the turning point, and it ended up being for the entire match.
"I played a great breaker. Got off to a good start there. But coming back from 5-2 in the first set, it was clearly big tonight."
Federer has now won 14 out of 14 quarterfinals in Melbourne and has yet to drop a set in this year's tournament.
Looking ahead to his semifinal opponent Chung, Federer said: "He's incredibly impressive in his movement, he reminds me a lot of Novak the way he is able to slide forehand and backhand and use the hardcourt as a claycourt.
"He gets balls back and stays aggressive in defence, so I'm really excited to be playing him, he's got nothing to lose, I will tell myself the same and we'll see what happens."
Federer was broken in his opening service game and fell behind 2-5 before he broke back with a backhand in the ninth game to send the first set into a tiebreaker.
He put the foot down and careered to five set points before taking the tiebreaker with an audacious drop shot.
He continued to put the squeeze on the Czech and broke him in the eighth game and served out for a two sets to love lead after 90 minutes.
Both players exchanged breaks early in the third set before Federer reeled off a signature backhand winner to break again in the fifth game.
He consummately served out for the match for his 20th win in 26 meetings with Berdych.
"I had a good chances, a couple of set points," Berdych said. "Then he just got more confident after he saved the first set. Then it was very difficult with him again."
Federer is coming off an extraordinary 2017, when he won a fifth Australian Open title and a record eighth at Wimbledon, after returning from an injury lay-off.
The 36-year-old is bidding to win his 20th Grand Slam title and is the oldest man to reach the semi-finals in Australia since Ken Rosewall (42 years) in 1977.
It was in Melbourne a year ago where he lit the fuse on his late-life tennis renaissance, beating Berdych, Kei Nishikori, Mischa Zverev and Stan Wawrinka before downing great rival Rafael Nadal in a five-set final classic. - AFP / Reuters
Norwegian doctor Gilbert, who had treated patients during the 1982 Israeli invasion of Beirut and later in Palestinian territories, speaks about his new mission
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