Australia, New Zealand lay down markers
England's George Burgess scores a try during the 2013 Rugby League World Cup group A match between Australia and England at the Millennium Stadium in Cardiff, south Wales on October 26, 2013
The Kangaroos produced a shaky opening 20 minutes in ceding a two-try 10-0 lead to England, but hit back with three converted tries before the half-time hooter.
A fourth try just minutes into the second period gave the Australians enough breathing space despite England scoring two more tries in the final 28-20 scoreline at Cardiff's Millennium Stadium.
It was a similar story for New Zealand against Samoa, the Kiwis crossing for four early first-half tries and then three in the second period to effectively wrap up the game, only to ease up and let the South Sea Islanders back in for four tries of their own in a thrilling second-half.
Kiwi winger Manu Vatuvei sealed the first hat-trick of the tournament to ensure New Zealand's 42-24 victory in a game that featured gruesome hits aplenty in front of a sell-out Warrington crowd.
Australia coach Tim Sheens, whose team are next up against Fiji on Saturday - while England play Ireland, acknowledged that his side had been rocked by the host side's impressive opening.
"I won't take away from the English performance," Sheens said. "They came out aggressively and scored from their first appearance near our line.
"England scored early, which probably rocked us a bit. We had two or three fundamental errors in our own half, which you just can't afford in Test matches.
"We have got some work to do, but England certainly came out to play. Given the issues they've supposedly had this week, I think they performed really well.
"The team they put out was a big strong side. They came up with some big plays, and it took a good effort from our guys."
Testy England coach Steve McNamara had enjoyed a rocky build-up to the match, Gareth Hock receiving the axe for a drinking session after their shock pre-tournament warm-up loss to Italy.
The defeat means England have a potentially harder path to the final, with a likely meeting against New Zealand in the semi-finals.
And star loose-forward Sam Burgess, who made history when lining up with twin brothers Tom and George, faces a ban after being placed on report for a nasty swinging arm into the face of Sam Thaiday.
"We started the game superbly and played with some great energy with the ball, but we gifted a lot of possession to the opposition and gave a lot of penalties away," McNamara said.
"I've always thought we have a team that is capable of potentially winning this competition if it concentrates and plays to its best, and it has to do that in every game.
England captain Kevin Sinfield added: "The group we have got is going to get better, a whole lot better.
"We have a strong squad, and if we are good enough over the next couple of weeks, hopefully we will get another shot at Australia.
"There are some tough games in front of us, but we are ready to rip into training again and make sure we turn up again next Saturday."
Kiwi coach Stephen Kearney was not left too deflated by the way his side won, although he said the defensive lapses that marred the second-half would be addressed in training this week ahead of Friday's match against France in Avignon.
"They gained the momentum," Kearney said. "We dropped some ball and touched it a couple of times whilst they had the footy.
"We didn't see a great deal of possession for 20 minutes there and, to their credit, I thought they played with a great deal of energy and enthusiasm and consequently put some tries on us."
Other results on the opening weekend saw Italy follow up on their shock warm-up victory over England by walloping Wales 32-16 while France pipped Papua New Guinea 9-8.