The defending world and Olympic champions survived a small scare. The Americans trailed Finland 2-1 heading into the third period, but rallied for a 6-2 victory in Thursday's marquee matchup in Espoo.

After a strong start, the host Finns couldn't keep up the pace, which is traditionally an issue against the dominant North American teams. Finland has only beaten the Americans once at this tournament (1-0 in overtime in 2008).

"I think we played a really good first two periods, but with the third one, we can't be happy," said Finnish captain Jenni Hiirikoski.

U.S. captain Kendall Coyne Schofield led the way with a goal and two assists, and Hilary Knight and Alex Carpenter had a goal and an assist apiece. Melissa Samoskevich, Brianna Decker, and Annie Pankowski also scored for the Americans.

"It was a tough start," said Coyne Schofield. "It's not the way we want to start a tournament and represent Team USA. But I think coming out in the third, we proved the game we can play. At the end of the day, we need to play a complete 60 minutes."

Elisa Holopainen and Petra Nieminen replied for Finland.

"I think we need to watch video and then figure out what happened," said Finnish goalie Noora Raty. "We played a really good 40 minutes, and then I don't think they scored five because they were good -- I think they scored five because we were bad. We were just flat for all the 20 minutes in the third."

The Americans are gunning for their fifth consecutive Women’s Worlds gold medal. Their next big test comes against archrival Canada. The Canadians last won the Women’s Worlds in 2012. All 18 Women’s Worlds finals, dating back to 1990, have pitted the North American superpowers against each other.

"It's going to be awesome," said Knight. "I'm excited for the fans. They get a great game, whether they're here in the stands or back home. Obviously for us to represent the country on the world stage against one of our biggest opponents is a lot of fun. We're looking for a good battle."

In the opener, Raty had a heavier workload than the U.S.'s Alex Rigsby, as shots favoured the Americans 45-23.

Before this home-ice tournament, Finnish coach Pasi Mustonen said he wanted his youthful fourth line to be the world’s fastest fourth line. That trio got Finland off to a great start with an electrifying goal off the rush at 9:28.

Viivi Vainikka burst into the American zone on right wing and centered it to Holopainen, a fellow 17-year-old. She fed it left to the 21-year-old Hakala, who sent it back to Holopainen, and she scored from the doorstep.

"I thought they were our best line," Raty said. "So maybe the older players should watch how they played and kind of get energy from that line. They have a lot of energy going on right now."

With 2:12 left in the first period, Coyne Schofield knotted the score. The Americans were playing 6-on-5 with a delayed penalty coming up to Finland. The speedy captain, who made headlines with her history-making participation in January's NHL All-Star Skills fastest skater competition, looped in from the center point and whipped a high shot past Raty.

"Noora's obviously one of the best goalies in the world, if not the best," said Coyne Schofield. "We had traffic in front, which helped. A great wide pass from Hilary opened up the lane for me to shoot the puck."

At 11:18 of the second period, Nieminen re-ignited the crowd of 4,046. She took a great Hiirikoski pass, powered past veteran U.S. defender Kacey Bellamy into the high slot, and zinged one past Rigsby on the stick side for a 2-1 lead on the power play. Bellamy was called for hooking on the play, but the Finns couldn't capitalize with the ensuing advantage.

Then the American floodgates opened up like Niagara Falls in the third period.

At 3:10, the U.S. tied it up again as Samoskevich surprised Raty with a long wrister to the stick side. The Americans took their first lead at 4:51 when a forechecking Hannah Brandt jarred the puck loose behind the Finnish net and Knight hammered it home.

The U.S. power play came to life at 7:38, with Carpenter skimming the puck past Raty's left skate with traffic in front. Mustonen argued there was goalie interference, but to no avail.

Of Carpenter's return to Team USA after being left off the 2018 Olympic team, Coyne Schofield said: "She's definitely a marquee player in the women's game, so it's awesome to see her back."

Decker made it 5-2 at 11:35, taking a pass from Coyne Schofield and coolly beating Raty with an in-tight backhand move.

"I'm glad we showed up in the third to really come out and compete for the pucks," said Knight.

Mustonen pulled Raty multiple times in the dying stages in search of a spark, but it just wasn't going to happen. Pankowski rounded out the scoring with 2:31 left.

Espoo-born hockey legend Jere Lehtinen, inducted into the IIHF Hall of Fame last year, presented the Best Player of the Game award to Holopainen. Coyne Schofield was honoured for the Americans.

Finland has brought back 19 players from last year’s Olympic bronze medal-winning team. In a recent interview with Ilta-Lehti, Mustonen said Finland is icing its best women’s team ever in this home-ice tournament. There is still time for his assessment to bear fruit.

"It doesn't matter if we lose 10-0 or win 10-0 these first four games," said Raty. "All that matters is the quarter-finals. So we'll take the good things and then move forward."

The Finns’ next game on Saturday is a rematch of their 2018 Olympic bronze medal game, in which they defeated the Russians 3-2.

"They have a lot of individual skills," Hiirikoski said. "They are good in the offensive zone. I think it's going to be a fun game on Saturday."

The opening ceremonies featured an all-female figure skating exhibition and local minor hockey players. Emma Terho, the former Finnish national captain and an IOC member, and Zsuzsanna Kolbenheyer, an IIHF Council member and head of the IIHF Women’s Committee, welcomed the world to Espoo and declared the 2019 IIHF Ice Hockey Women’s World Championship officially open.