Roared on by their fans in Busan, South Korea came from behind to beat Argentina 3-2 on Sunday in the first round of Davis Cup qualifying.
Elsewhere record 32-time winners the United States cruised to victory in Hungary, Belgium won in Bulgaria and the Czech Republic ensured victory over Sweden.
Argentinians Guido Andreozzi and Federico Agustin Gomez opened the day by putting the visitors 2-1 ahead, beating Nam Ji-sung and Park Ui-sung 6-3, 7-5 in the doubles.
Thiago Agustin Tirante then went a break up in the deciding set against Kwon Soon-woo, ranked 248 spots lower, but Kwon fought back to win 6-4, 4-6, 6-3 and level the tie.
Hyeon Chung breezed through the high-pressure decider with a 6-4, 6-3 victory against Marco Trungelliti.
Kwon, who is still completing Korean military service, said he was motivated by the support.
"They cheered so loudly," he said. "It really helped me stay focussed."
Hyeon Chung's moment for his country 🇰🇷
— Davis Cup (@DavisCup) February 8, 2026
The moment he takes his nation to September Qualifiers Second Round. #DavisCup pic.twitter.com/95dR8E3JQP
None of the Argentina team had played a Davis Cup rubber before. The 2016 champions have eight players ranked in the ATP's Top 100 but took only one, Tirante, to South Korea.
In the second round, the South Koreans will face the winner of the clash between India and Netherlands for a place in the Davis Cup Final 8.
India led 2-1 in Bengaluru after Yuki Bhambri and Dhakshineswar Suresh romped through two tie-breaks to beat Sander Arends and David Pel 7-6 (7/0), 3-6, 7-6 (7/1).
In Tatabanya, Hungary, Christian Harrison, the Australian Open doubles champion, paired with Austin Krajicek to claim the clinching point with a 6-4, 3-6, 6-3 victory over Fabian Marozsan and Zsombor Piros.
Harrison, making his Davis Cup debut, said: "I had such a good time this week, I already forgot about" the Australian Open.
In Plovdiv, Belgium's Sander Gille and Joran Vliegen beat Bulgarian pair Alexander Donski and Pyotr Nesterov 7-6 (7/5), 7-6 (7/3) in the morning doubles to secure a winning lead.
"We knew it was going to be a very difficult match," said Vliegen. "They have great talent, young guys. Happy to get the points and the qualification for Belgium."
In France, Benjamin Bonzi and Pierre-Hugues Herbert beat Slovaks Milos Karol and Lukas Klein 6-2, 6-3 to put the home team 2-1 up.
Elsewhere, Ecuador led 28-time champions Australia 2-0 in Quito.
Germany, Austria, Chile, Croatia, Britain and Canada had locked up round two qualifying places earlier in the weekend.