LONDON >> Katie Taylor stepped through the ropes and into the madness, beaming at thousands of flag-waving, face-painted Irish fans raucously celebrating her Olympic boxing victory.

The pound-for-pound world champion clenched her fists and roared right back at them.

The debut women’s tournament stopped being just historic and started getting passionate in the quarterfinals Monday. Twelve fighters made sure they’re heading home with medals, but everybody still wants to upgrade.

“It’ll only be a relief if I’m on the top of the podium with the gold medal and nothing else,” the Irish lightweight said after riding a dazzling swell of fan support to a 26-15 win over Britain’s Natasha Jonas. “I’m just concentrating on my next fight. No one is happy with a bronze medal.”

But boxing fans seemed thrilled after the second straight day of highly entertaining, evenly matched bouts in a sport that was banned in Britain until 1996. The ExCel arena officials measured the decibels and said it was their loudest crowd so far — and loudest of all while Taylor picked apart Jonas in their rivalry bout.

“I’ve never experienced an atmosphere like this before,” Taylor said. “It’s been incredible.”

Flyweight Marlen Esparza and middleweight Claressa Shields also clinched the U.S. team’s first two boxing medals in London. Esparza patiently outboxed Venezuela’s Karlha Magliocco, and the 17-year-old Shields closed furiously in an 18-14 win over Swedish veteran Anna Laurell.

The Americans also emerged in awe of the atmosphere in this Olympic debut.

“I had to keep myself calm out there,” said Shields, who could still hear instructions from her personal coach, Jason Crutchfield, shouted from the stands. “I didn’t want to be overanxious, but it was kind of like, ‘Wow.'”

Women’s boxing pioneer Mary Kom of India and Britain’s Nicola Adams also secured medals in this brisk tournament, which only began Sunday with the landmark first bouts.

Top-seeded flyweight Ren Cancan of China advanced, but top-seeded British middleweight Savannah Marshall was upset by Kazakhstan’s Marina Volnova, Shields’ next opponent.

Esparza restored respectability to the American team, which hadn’t won a bout inside the ring in eight days. The American men had lost eight consecutive fights before welterweight Errol Spence’s apparent loss last week was overturned by amateur boxing’s governing body on appeal.

Esparza had little trouble with the wild-swinging Magliocco, battering her with counterpunches and then getting out of the way. The crowd preferred Magliocco’s undisciplined aggression, but Esparza didn’t win six national championships by brawling.

The 23-year-old Cover Girl model from Houston must face Ren in her next fight, but believes her tactical approach can work against anybody.

“It feels good, and I know that the USA needed it badly,” Esparza said. “I thought the crowd was going to freak me out a lot more than it did. I’ve never fought in front of something like that.”

Shields rallied from a second-round deficit against Laurell, who fought at the first women’s world championships 11 years ago. The teenager from Flint, Mich., has uncommon velocity on her punches, and Laurell used her superior reach to stay outside for the first two rounds until her legs tired and Shields pounced, unleashing multiple big shots.

“I definitely don’t feel like I fight like a girl,” Shields said. “I’m boxing out there. I just happen to hit hard.”

But the main event was Taylor’s electrifying victory over Jonas, just the second loss by a British boxer in their home Olympics — until Marshall was shocked an hour later. Hundreds of Irish fans showed up early to cheer Taylor, a reigning world champion since 2006 and the Irish team’s flagbearer in the opening ceremony.

Taylor came through in front of a crowd singing her name, repeatedly punishing the impressive Jonas with a stiff right hand and defensive skills that rival any male Olympians.

Jonas gave Taylor a strong fight in the first two rounds, landing her right hook and avoiding most trouble. But Taylor, a former player on Ireland’s national soccer team, is athletic and relentless, and eventually picked apart Jonas’ defense. Jonas took standing eight counts in each of the final two rounds after absorbing brutal combinations from Taylor.

“She’s still the best,” Jonas said. “She comes out on top every time. My hat’s off to her. There’s nothing else. … I could have thrown the kitchen sink (at her), maybe drove the bus into her. It didn’t work.”

Second-seeded Nadezda Torlopova of Russia won the final middleweight fight, and the grateful crowd gave one last ovation.

“When you see women’s boxing at the highest level, after this kind of a performance, I don’t know how you can argue we don’t belong in the Olympics,” Jonas said.