Argentina hung on in the face of determined Scotland pressure to win their quarter-final 19-13 in Paris on Sunday and reach the last four of the Rugby World Cup for the first time.
In by far the least attractive match of the quarter-finals weekend, the tiring Pumas defended their tryline tooth and nail against a last-ditch Scottish onslaught to earn a semi-final against South Africa.
"We were very tired and Scotland played really well. We stuck with it, we wanted to be in our first semi-final and we are," Pumas captain Agustin Pichot told ITV television.
Argentine players and fans, some beating drums, became locked in a frenzy of soccer-style celebration as the Pumas, unlikely semi-final candidates when the tournament started a month ago, notched a historic fifth World Cup victory in a row.
The teams scored one try apiece, number eight Gonzalo Longo for Argentina in the first half and replacement scrumhalf Chris Cusiter for the Scots with 16 minutes remaining.
The difference between the sides in the end were six of the points from the boot of centre Felipe Contepomi, whose three penalties and a conversion took his tournament tally to 64 points.
The Argentines, notching their sixth successive victory over Scotland, had a nervous final quarter of an hour as Scotland, their dream of a second semi-final since 1991 ebbing away, threw everything they had into a potential match-winning try.
In the poorest of the four quarter-finals following Saturday's exciting upset victories by hosts France and defending champions England to reach the other semi-final, the packs dominated from the off in a battle of attrition.
Scotland went ahead with a Dan Parks penalty from just inside the halfway line after Contepomi had missed his first effort.
Contepomi, however, put the Pumas level and then 6-3 up with successive penalties either side of the half hour.
Then Argentina made the breakthrough when Longo charged down an attempted clearance deep in the Scottish half by wing Sean Lamont, chased the loose ball and beat two Scots to the touchdown. Contepomi converted.
Chris Paterson reduced Argentina's lead to 13-6 with a penalty just before halftime.
Pumas flyhalf Juan Martin Hernandez had a poor first half which might have started brightly if his drop goal attempt in the opening minute from some 35 metres had not sailed just wide of the upright.
The flyhalf's kicking from hand was wayward and when he tried to run the ball he was usually stopped dead or slipped on the damp turf.
But there was a marked improvement after the interval including a fine left-footed drop goal in the 55th minute that gave Argentina a seeming unassailable a 19-6 lead.
However, with most of the fresh Scottish replacements on the field, Scotland launched a counter-attack down the left and the ball went blindside out of a maul with Cusiter darting over in the corner.
Paterson maintained his 100 percent kicking record in the tournament with the conversion and when Hernandez missed a drop attempt minutes later the scene was set for a dramatic denouement.