Cameron Norrie and Dan Evans both battled to give Great Britain a 2-1 win over France in their Davis Cup tie.
British number one Norrie claimed a gutsy 6-2 7-6 (10-8) win over Arthur Rinderknech to seal the best-of-three tie in Innsbruck, Austria.
Evans had earlier beat Adrian Mannarino 7-5 6-4 in a high-quality encounter.
However, Rinderknech and Nicolas Mahut claimed a consolation 6-1 6-4 win over Joe Salisbury and Neal Skupski in the doubles rubber.
The tie is Great Britain's first in Group C, with the top teams from each group and the two best runners-up qualifying for the quarter-finals.
Evans started strongly as he fought for one hour and 55 minutes to beat the experienced Mannarino.
Norrie then overturned a 4-1 deficit in a close second-set tie-break to see off French number one Rinderknech.
Great Britain will be guaranteed qualification as group winners if they beat the Czech Republic tomorrow.
Norrie, 26, has had a stunning season, including winning the Indian Wells Masters and rising to 12 in the world rankings.
His quality showed against Rinderknech, with the Briton recovering from a nervy start to reel off five games in a row and take the first set.
He was helped by 19 unforced errors from Rinderknech, but the Frenchman tightened his game in the second set.
Rinderknech found his way out of a service game at 3-3 that saw nine duces and three break points for Norrie, holding on well enough to force a tie-break.
Norrie's forehand broke down as the 26-year-old Frenchman raced to a 4-1 lead, but the Briton clung on and was rewarded for some brave shot-making when he found himself set point down.
He saw two match points come and go before eventually securing victory in two hours and six minutes.
"All credit to the guy to make it to the tie break and I was fortunate to sneak through there," Norrie said.
Evans continues good form
Evans too has enjoyed a strong season, winning his first ATP title and reaching a career high of 22 in the world.
Both he and Mannarino showed signs of nerves, with Evans slipping to 0-30 down on serve four times in the opening set.
Evans was broken to love as he served for the set at 5-3, but his aggressive play allowed him to hit back and eventually close out the set with a thumping serve that Mannarino could not return.
Mannarino cut a frustrated figure during the second set, frequently gesturing to his captain and the empty stands as Evans found his rhythm on serve.
Evans peppered the forehand corner, putting Mannarino under constant pressure, and it showed as the Frenchman fluffed a volley that ultimately allowed the Briton to break and serve for the match.
There were no signs of his struggles in the first set, with Evans serving out to love before turning to roar in celebration at the GB support box.
"I thought about the match all week - I was very nervous beforehand," he said.
"I wanted to set it up for Cam. All the pressure is on the other guy to get it to 1-1 and that was my job."
The Davis Cup is being held across three cities, with the semi-finals and final being held in Madrid from 3 to 5 December.
Teams play two round-robin ties, each featuring two singles and one doubles rubber all played over best-of-three sets.
The top teams from each group and the two best runners-up qualify for the quarter-finals.