WALLABY wing Adam AshleyCooper will take the plaudits for his hat-trick of tries to put Australia into their first World Cup final since 2003, but it was a monumental second-half defensive effort at Twickenham that saw his team over the line.
Argentina will rue a poor first half where they conceded three tries, two of them softer than a down pillow, that put them on the back foot from the outset.
But they made a fist of attempting a comeback, pulling to within seven points of the lead with eight minutes to go.
Ashley-Cooper’s third try finally slayed the Pumas, with the Wallabies winning 29-15.
Australia will face New Zealand in next week’s World Cup final for the first time.
The winner will also become the first three-time winner of the Webb Ellis trophy.
It promises to be a mouth-watering contest between two sides intent on attack but brilliant on defence as well.
For the Pumas, their prize is a date with the Springboks in the bronze medal match on Friday, and in both cases the match serves as a season-decider between the sides.
Earlier this year Australia beat the All Blacks in Sydney and lost the return in Auckland, while the Pumas toppled the Boks in Durban before losing the return in Buenos Aires.
Ashley-Cooper sealed victory in the 72nd minute thanks to a wonderful, weaving run by wing Drew Mitchell.
But for 15 minutes prior to that score, Australia had been grimly hanging on as the Pumas came at them in waves.
Wallaby flank Scott Fardy was monumental in breaking down several attacks that, had the wall broken, could have led to a different outcome.
Nicolas Sanchez’s five penalties took Argentina to within a converted try of the lead at 22-15, but they could not unbuckle the yellow defensive belt.
Argentina’s desire to up the tempo early on, which had worked so well against Ireland in the quarterfinal, played into Australia’s hands.
It led to Australia’s first 14 points inside the opening 10 minutes, putting the Pumas in a deep hole before they had even worked up a sweat.
The Wallabies like nothing more than an up-tempo game, feeding off mistakes and inaccuracy. With David Pocock leading the Wallabies’ predatory back row, Argentina struggled to find the rhythm they had against Ireland because they couldn’t consistently claim quick ruck ball. Pocock made two first-half steals alone.
The Pumas also had several first-half setbacks that knocked them off kilter. Captain Augustin Creevy, who came into the game with a suspect quad muscle, limped off midway through the first half after an anonymous 27 minutes.
That came moments after lock Tomas Lavanini was yellow-carded for a dangerous tackle, which was harsh to put it mildly. Lavanini slightly mistimed a chop tackle and there was nothing malicious in it.
Chop tackles have not been penalised all World Cup but referee Wayne Barnes decided the 46th of 48 games was the time to start. It cost Argentina seven points while Lavanini stewed in the sin bin.
Pumas star wing Juan Imhoff also staggered off the field after a sickening, but inadvertent, thump from Israel Folau’s knee.
It became worse, with playmaking centre Juan Martin Hernandez hobbling off early in the second half.