After falling behind to a second-half header from Ladislav Krejci, the Koreans rallied through goals from Hwang In-beom and Oh Hyeon-gyu to secure three crucial points in Guadalajara.
"Before the match I gave two messages: not give up until the end and unite as one," he told a press conference. "Whether on the pitch or not, we need to play as one team."
The victory came despite an uncharacteristic off-day for captain Son Heung-min, who missed five chances in the first half alone before being replaced by eventual match-winner Oh.
Despite the misfiring performance, the coach was quick to defend his veteran forward.
"Son is our best player and is also a very stable captain. We believe that Son did his best," the coach said, though he added the team must "brush up" on finishing their chances.
South Korea are tied on three points with Mexico at the top of the group, setting up a high-stakes clash against the tournament co-hosts on June 18.
"Both teams scored three points ... the next match will be very important," Hong said.
The 2026 World Cup will be held from June 11th to July 19th in the United States, Canada and Mexico. The tournament will feature 48 national teams and will be played in 16 modern stadiums.
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