Iran produced a resolute defensive display to snatch a 1-0 away win over South Korea on Tuesday and qualify for the World Cup finals in Brazil.
Despite the defeat, the Koreans also qualified for the finals after they edged Uzbekistan - 5-1 winners over Qatar on Tuesday - for the runners-up spot on goal difference.
Forward Reza Ghoochannejhad was Iran's hero, latching on to an error by defender Kim Young-gwon to score the winner in the 60th minute with the visitors' only real chance of a one-sided match in Ulsan.
Iran coach Carlos Queiroz punched the air in delight at the final whistle after their third qualifying win in June sealed a fourth finals appearance.
The under-pressure Portuguese had traded verbal volleys before Tuesday's Group A clash with Korean counterpart Choi Kang-Hee, who had vowed to beat Iran and force them to watch the World Cup on television after being "badly treated" in the reverse fixture in Tehran last year.
Choi's side showed the same intent by making a fast start at the Ulsan Football Stadium, with lanky striker Kim Shin-wook going close to giving them a fifth-minute lead, but his volley flew just over the bar.
Kim was part of an attacking lineup employed by Choi with Son Heung-min, Lee Dong-gook and Ji Dong-won all starting, but the home side were guilty of using too many long balls for the tall striker rather than mixing up their play.
Iran knew a draw was likely to be enough to qualify unless Uzbekistan could score a four-goal win over Qatar, so they chose to sit back and allow Korea plenty of possession. But the home side failed to create many chances.
The Koreans had a strong appeal for a penalty five minutes before halftime, when midfielder Lee Myung-joo raced clear only to be brought down by Iran fullback Khosro Heydari and goalkeeper Rahman Ahmadi, but the referee awarded a goal kick.
Korea were sluggish at the start of the second half, and Iran grew in confidence before taking a shock lead.
Korea defender Kim Young-gwon missed his kick as he attempted a back-pass to his keeper, and Ghoochannejhad raced through to curl home a left-foot shot.
Choi introduced AFC player of the year Lee Keun-ho as the hosts searched for an equaliser against an Iran team that had conceded just two goals in their previous seven qualifiers.
Kim Young-gwon came close to making up for his error when he fired a sharp shot in the 76th minute that was well saved by Ahmadi, while his glancing header two minutes from time sailed just wide.
Substitute Lee had half the stadium on their feet thinking he had scored a 94th-minute leveller but his header edged past the far post with Ahmadi motionless.
While the Iranians celebrated, the Korean players waited for news of Uzbekistan, who cruised past Qatar 5-1 but ultimately fell two goals short of overhauling Korea on goal difference, allowing them to rejoice at a ninth World Cup finals appearance.