Kim Lammers scored twice in her Olympic debut for the Netherlands. Lammers is the most-capped Dutch player, having played her first international game in 2002, but she was not selected for the Athens 2004 team and a knee injury forced her to miss the Beijing Olympics.
"It's great to score goals in this big tournament," Lammers said.
Captain Luciana Aymar scored twice in Argentina's win; losing 2008 finalist China beat South Korea 4-0 and New Zealand upstaged three-time champion Australia 1-0 in the opening match of the tournament.
Britain, considered a strong outsider, scored four first-half goals against Japan then relaxed in a goalless second half.
"I think I keep pinching myself and I look around and see London all over the boards. It's an incredible turf I'm playing on with some of my best friends," said Alex Danson, who scored twice for Britain. "It feels incredible to win the game, I don't mind who scores as long as we score one more than the opposition."
In the day's last match, Germany beat the United States 2-1, holding off a strong second-half performance by the Americans.
Hockey is being played on the Riverbank Arena's newly built bright blue pitch, with a pink border. It is the first time an Olympic hockey tournament has been played on a pitch that is not green.
The garish colour scheme is designed to contrast with the fast-moving yellow ball, making the game easier to play for competitors and easier to follow for spectators. They also reflect the London Olympic colours.
Earlier Sunday, Cathryn Finlayson scored in the third minute to give New Zealand its victory over old rival Australia.
Australia's last gold medal was at home during the 2000 Sydney Olympics. New Zealand, meanwhile, is improving after failing to win a match at the 2008 Beijing Games.
New Zealand had the ball in the Australian net in just the second minute, but the umpire had already blown for a short corner for an earlier offence. From the corner, Finlayson scored her 18th international goal.
Australia threw everything into attack in the second half but could not break down the stubborn Kiwi defence and could have gone further behind had it not been for a great low save by goalkeeper Toni Cronk on a Charlotte Harrison backhand shot.
"We created a lot of chances in the first half," said New Zealand captain Kayla Sharland. "We scouted them a lot, we watched a lot of video footage of them."
In Sunday's third match involving close neighbours, China's lead goal scorers Yudiao Zhao and Yibo Ma both contributed to the goal count. Ma opened the scoring with a penalty corner in the 26th minute and Zhao following up with a field goal 16 minutes into the second half.
The 23-year-old Zhao made her international debut in 2007, and in 2010 she was awarded Young Player of the Year by the International Hockey Federation.
"Beijing was my first Olympic Games and four years have now passed, and I know I have improved a lot during that time," she said.
China midfielder Hongxia Li added a third only three minutes after Ma's strike, making the most of an awarded penalty stroke.
Ma scored a second penalty corner in the closing minutes of a foul-heavy second half in which China forwards Baorong Fu and Lihua Gao saw themselves temporarily suspended from play.
"It is a beautiful feeling," South Korean-born China coach Kim Sangry-ul said.