Belgian brothers Kim and Ronny Huybrechts emerged victorious from a fiery and dramatic last eight clash with fellow former finalists Australia, for whom Simon Whitlock and Paul Nicholson suffered an agonising loss.
The Australians had seemed set to power into the last four when Whitlock defeated Ronny Huybrechts 4-2 in their Singles tie and Nicholson took a 3-0 lead against the younger brother in the second contest.
However, Kim Huybrechts clawed his way back into the game before punishing Nicholson for six missed match darts across two legs to force a decider, which he won on double eight to take the clash into a Doubles decider.
With both nations fired up, Belgium held throw twice only for Nicholson to twice land the winning double as Australia levelled, but Kim Huybrechts took out 105 for a 3-2 lead before Ronny Huybrechts finished 86 on the bull to claim victory.
"In the Doubles I know me and Ronny can do serious damage and it was an emotional Doubles game, so tense, but we're on top of the world," said Kim Huybrechts.
"Paul is very similar to me, we're both emotional when and very enthusiastic when we play. He was giving it loads when he went 3-0 up and I needed to get the crowd on my side and I think it got to him a bit and he missed match darts.
"In the Doubles, Ronny was brilliant and the 86 was a massive shot for the match, so big respect for that.
"Now we have to focus on the next game because we have to play this evening, so we have to relax now, forget about this and prepare for the semis now."
Belgium will now face England in a repeat of the 2013 World Cup of Darts final, after Phil Taylor and Adrian Lewis produced two superb individual displays to knock out hosts Germany.
Taylor averaged over 104 in his 4-1 win over Jyhan Artut, whose only leg came with a fine 12-darter, before Lewis posted a 105 average in his brilliant 4-0 whitewash of teenager Max Hopp, which was book-ended by two 13-darters.
"That's a good win for us," said Lewis. "Jyhan played great against Phil and I had a tough contest against Max Hopp, but I hit him early on and kicked on from there.
"We're through to the business end of the competition and we're practising really well, so if we can put it all together there's no reason why we can't win it."
The other semi-final will see reigning champions Netherlands face Scotland, who won through to their first semi-final in the five-year history of this event with a 2-0 defeat of Hong Kong.
World Champion Gary Anderson kicked off the tie with a 4-2 win over Ting Chi Royden Lam, before team-mate Peter Wright matched that score in his defeat of Scott MacKenzie.
"I've been making hard work of things but hopefully I'll come good tonight," said Anderson. "I don't think I've played Royden before and he was nervous before the game, but he did alright and he'll learn from that.
"It's been a tournament where we've been playing against players we don't know, but in the semi-finals we know what to expect."
Dutch pair Michael van Gerwen and Raymond van Barneveld needed a Doubles decider in their tie against Northern Ireland, but repeated last year's 4-0 win at the semi-final stage against Brendan Dolan and Mickey Mansell with another superb whitewash.
Van Gerwen had defeated Dolan 4-2 in their Singles tie before Mansell produced a superb display to overcome van Barneveld in a deciding leg, but the Northern Irish pair had no answer to a 107 average from their opponents in the Doubles game.
The £250,000 tournament concludes on Sunday night, with the semi-finals followed by the final at the Eissporthalle in Frankfurt, as four of the top five seeds in the tournament compete for the title.
bwin World Cup of Darts
Sunday June 14Afternoon Session
Belgium 2-1 Australia
Scotland 2-0 Hong Kong
England 2-0 Germany
Northern Ireland 1-2 Netherlands
Evening Session (8pm local time)
England v Belgium
Scotland v Netherlands
England/Belgium v Scotland/Netherlands
The Semi-Finals will be played as two best of seven leg 501 Singles matches, with both nations nominating the order in which their players play. In the event of both nations winning one Singles match apiece, a best of seven leg 501 Doubles match will be played to decide the tie.
The Final will be played as two best of seven leg 501 Singles matches, with both nations nominating the order in which their players play the first two matches, followed by a best of seven leg 501 Doubles match and then Reverse Singles matches. The first team to win three games is the winner.