George Hincapie won stage 15 of the Tour de France to become the seventh American and the first team-mate of Lance Armstrong since 1999 to claim a stage victory in a successful day for the Discovery team.
Six-time winner Armstrong fought off the threat of CSC's Ivan Basso to strengthen his grip on the yellow jersey, while Michael Rasmussen was well supported by his Rabobank team-mates as he retained the polka-dot jersey.
There was no let up in the hot conditions as the riders took on the most testing stage of the Tour, from Lezat-sur-Leze to Saint-Lar-Soulon.
No fewer than six Pyrenean climbs lay ahead of the 160-strong group on Sunday morning, including a category two, four category ones and one 'Hors' category climb to be negotiated.
Many riders sported white armbands with 'Fabio' written on them as a tribute to Fabio Casartelli, a team-mate of Armstrong's who died after crashing during stage 15 of the 1995 Tour.
Proceedings began tentatively, with the peloton quickly chasing down early breakaway attempts.
It was not until the 17km mark that ten escapees appeared to have successfully gained a lead, only for the peloton to once again reel in the group, which included Colombian Santiago Botero and Spaniard Jose Luis Arrieta.
However, Rabobank's Michael Boogerd then launched another attack, prompting a breakaway of 14 riders, which proved to be the day's first decisive moment.
The escapees' lead grew rapidly as the peloton, containing Armstrong and his closest competitors, showed no signs of chasing down the group.
Within an hour the 14 riders had established an 11 minutes and 40 seconds gap over the chasing peloton in what was, at that point, the biggest leading margin of any escape on the 2005 Tour.
As the leaders approached the first of the day's climbs, Michael Boogerd along with fellow team- mates Erik Dekker and Karsten Kroon ensured Rabobank absorbed the points to protect the strong hold on the polka-dot jersey of their Danish colleague, Michael Rasmussen.
As the riders entered Spanish territory, with the gap between the leaders and the peloton at over 18 minutes, CSC leader Basso suffered a rear tyre puncture but was recovered into the peloton with the help of his team-mates.
Finally, the escape group began to break up as they prepared to take on the final four climbs.
Mikel Astarloze, Pineau and Bertogliati fell away as Kroon set the pace over the summit of the Col du Portillon, beyond which the lead group was reduced to 10 riders.
Kroon's speed was too much for three of the leaders who fell back before Kroon then dropped away from the group on approach to the summit of the Peyresourde climb, having done his duty for Boogerd.
Kroon's departure from the leading pack left Boogerd and Hincapie up against Oscar Pereiro, Laurent Brochard, Oscar Sevilla, and Pietro Caucchioli as they contested for a place on the podium.
As the peloton headed for the summit of the penultimate climb - Col de Vaz-Louron Azet - Basso finally launched an attack. Armstrong and Jan Ullrich, who duly gave chase, setting up an exciting finish to the stage.
Basso unsuccessfully tried to drop the Texan while Hincapie, Boogerd, Caucchioli and Pereiro pulled away from Sevilla and Brochard as the race entered its final six kilometres.
In the final 250m, it was between Hincapie and Pereiro at the front but the American showed his sprinting prowess to take an unexpected stage win before Basso led Armstrong over the line.
Hincapie showed his delight after being relieved of his duty to protect Armstrong in order to go for the win.
"I knew it was going to be a difficult day. (Discovery) gave me the go ahead and it was a dream come true for me today. A lot of people have asked me why I don't go and race for another team but this is the best team in the world and it was just amazing that I won."
Armstrong - who enjoys a lead of almost three minutes on second-placed Basso - was clearly pleased for his teammate, saying: "We have been riding together for about 20 years or so, so you can imagine what it means to me."