They looked the part for only a brief spell at the start of the second half, when retrieving one of the two goals scored by Tomas Rosicky, the Czech international who cost £8 million from Borussia Dortmund last summer.
But Arsenal, Cup winners four times under Arsène Wenger, broke out near the end with a fine individual goal by Thierry Henry, deservedly inflicting a first home defeat on their hosts since Benfica won in the Champions' League 21 matches ago. Even without the suspended Cesc Fabregas, they cut the midfield supply to Peter Crouch and Dirk Kuyt, Steven Gerrard's influence coming too late to affect the result.
Mathieu Flamini proved a solid deputy for the more flamboyant little Catalan and behind him Kolo Touré defended exceptionally. Henry, having had a gentle reintroduction against Charlton following his eight-match absence, seemed to find the going much harder here, but saved his best for the end.
"It was a determined, disciplined, well-organised performance," Wenger said with justification. "When Liverpool came back to 2-1 I was worried, because we had heavy legs, but Thierry killed the game." A disappointed Rafael Benitez had little to add, claiming: "We controlled the game for 35 minutes and then conceded two goals."
Slow to appreciate the importance of the Cup on his arrival in this country, Liverpool's manager learnt his lesson as last season's run gathered momentum on the way to Cardiff. Like Wenger, he picked what was effectively his strongest available side here with the exception of the goalkeeper. But whereas Arsenal's Manuel Almunia made the most of a rare opportunity, Jerzy Dudek did not and might reasonably have been faulted for the last two goals.
There had been an unreal air to the opening six minutes as the whole of the Kop held up red and white cards to form a giant mosaic and chanted "Justice for the 96" in support of those supporters who died at Hillsborough almost 18 years ago. Anyone whose view was obscured would have missed nothing, the first quarter of the game passing without incident.
Suddenly the game took off, after Xabi Alonso had been shown a yellow card by Steve Bennett for an alleged dive, even though it looked as if Gilberto Silva had clipped his leg. There was at last a threat on goal as Almunia had to turn away Kuyt's swirling cross and Peter Crouch volleyed over after taking Alonso's pass neatly on his chest.
Alonso's volley direct from Luis Garcia's corner was closer, and although Arsenal were beginning to move forward with greater purpose it was something of a shock when Rosicky struck twice in the space of eight minutes. For the first goal he set Alexander Hleb going on the right and met a low cross with a deftly curled shot over Dudek and high into the net. The second was equally impressive, though Liverpool's attempts to stop him were feeble. Receiving a short pass from Henry, the Czech wriggled in among four defenders, none of whom made a tackle before he drove the ball low beyond Dudek's dive.
Liverpool, a single point ahead of their visitors in the Premiership, predictably stepped up the pace attacking the Kop end after the interval, though some determined defending restricted the number of chances. Jermaine Pennant was unable to make much headway against his old club and Benitez must have been thinking of sending on Craig Bellamy when his team halved the deficit after 71 minutes.
Fabio Aurelio, who had replaced John Arne Riise, won a corner on the left from which Crouch nodded on and Kuyt, left unmarked inside the six-yard area, headed in. The Brazilian then met a diagonal cross from a resurgent Gerrard with a well-struck volley that fizzed past the far post. But with six minutes to play Henry came to life to score an outstanding goal and confirm victory. Latching on to a loose ball in the centre circle, he set off down the left, shrugged aside Jamie Carragher's challenge and ran on to beat Dudek.
The whole ground applauded when he was substituted, feeling his back, and Arsenal were granted an ovation at the final whistle on Merseyside's impressively dignified day in defeat. Wenger will return with a much weaker side for the Carling Cup quarter-final on Tuesday, making his priorities clear.