Two goals from Alex Danson helped Great Britain beat South Korea 4-1 to reach the Champions Trophy semi-finals.
Georgie Twigg touched in the opener and Danson's brace put Britain on top, before Helen Richardson scored a fourth after South Korea pulled one back.
Britain will face Germany, who are ranked third in the world, on Saturday (2030 GMT) for a place in the final.
"We're chuffed to bits. We're going to do our homework and come out fighting for that semi-final," said Danson.
She added: "We'll do our analysis on Germany and recover the best we possibly can, so when we come out we're just set to run."
South Korea had not won a Champions Trophy knockout game in seven attempts and Britain extended that miserable record with an excellent victory in the Argentine host city of Rosario.
And Britain advanced without the prolific Crista Cullen, who had netted in each of the three group games, managing to get on the scoresheet.
Twigg claimed the final touch to captain Kate Walsh's goalbound shot from a penalty corner before Danson scored twice, the second a superb reverse-stick strike, in quick succession.
South Korea's Lee Seon-ok scored with a penalty stroke after British keeper Beth Storry bundled over Park Mi-hyun.
But Storry redeemed herself with a stunning reaction stop to prevent South Korea narrowing the gap further in the last action of the first half.
Britain weathered a storm early in the second period as South Korea forced a succession of penalty corners to no avail.
And Richardson eased her side's nerves by sliding in to divert Walsh's strike from a penalty corner into the net.
Twigg added: "I'm so thrilled. We knew it was going to be tough, we went out there and fought our hearts out. We had to work really hard for the whole 70 minutes.
"It was a great drag-flick from Kate and I just cheekily put it in."
Hosts Argentina will play Olympic champions the Netherlands in Saturday's other semi-final. Organisers have swapped the semi-final start times, meaning Britain now face Germany at the earlier time of 2030 GMT on Saturday, while the Dutch and Argentines play in the later 2300 GMT slot.