Johnny Sexton's two-try turn dragged 14-man Ireland to the World Cup quarter-finals but Bundee Aki's red card in the 47-5 win over Samoa could end his tournament.
Ireland tries: Best, Furlong, Sexton (2), Larmour, Stander, Conway
Ireland conversions: Sexton (4), Carberry (2)
Samoa tries: Lam
Johnny Sexton's two-try turn dragged 14-man Ireland to the World Cup quarter-finals but Bundee Aki's red card in the 47-5 win over Samoa could end his tournament.
Ireland's bonus-point victory in Fukuoka sealed a safe passage to the last eight, whatever happens in Japan and Scotland's typhoon-threatened encounter on Sunday.
Joe Schmidt's men moved top of Pool A and booked a quarter-final against either New Zealand or South Africa, thanks to two tries from Sexton and scores for Rory Best, Tadhg Furlong, Jordan Larmour, CJ Stander and Andrew Conway.
Aki's red card for a high tackle on UJ Seuteni marred the victory, however, and now the centre born in New Zealand to Samoan parents will face a suspension.
The Connacht star had badly wanted to impress against his fatherland, but could now be banned for the remainder of the World Cup.
Ireland will not know their quarter-final opponents until the resolution of Sunday's Yokohama clash between the Brave Blossoms and the Scots.
World Rugby will rule on Sunday morning whether that match can beat Typhoon Hagibis and be staged as planned.
A cancellation would see the game ruled a scoreless draw and both teams awarded two points, with Scotland eliminated and Japan topping the pool.
Ireland would then face New Zealand on Saturday, October 19 with Japan taking on the Springboks the following day.
Schmidt's men were at least able to ride out the nation's first World Cup red card with precious little issue.
Aki's dismissal carried plenty of parallels with CJ Stander's red card against his native South Africa in 2016. Stander was left gutted to be sent off in his first match against his homeland, but even then Ireland prevailed, winning 26-20 in the first Test of that summer series.
So it proved in Fukuoka too, with Ireland moving on easily enough but still counting the cost.
A textbook penalty lineout maul handed Ireland the perfect start, with captain Best claiming the first try just three minutes in.
🙌☘️ FT: Ireland 47-5 Samoa - Joy for @IrishRugby with a quarter-final place secured in good style.
— Sporting Life (@SportingLife) October 12, 2019
👍 Jordan Larmour takes Man of the Match plaudits!#IREvSAM #ITVRugby #RWC2019pic.twitter.com/Al62xL8bGh
Samoa hooker Seilala Lam was sin-binned for a high shot on Jacob Stockdale, paving the way for Ireland to strike again.
Another penalty lineout maul pushed Ireland into the 22, and Furlong bulldozed through four defenders to claim a fine try.
James Ryan rescued Ireland with a stunning lineout steal in his own 22, and that set Ireland en route to try number three, with Larmour breaking the line and sending Sexton home.
Sexton's third conversion had Ireland 21-0 ahead and cruising at the end of the first quarter.
Despite Jack Lam squeezing in for a Samoa try Ireland were still comfortable - but then everything changed with Aki's red card.
The teak-tough centre of Samoan descent thundered into Seuteni, connected with his head - and was standing upright enough in the process to warrant a straight dismissal.
And so Ireland were left to battle more than 50 minutes with 14 men, in a huge test of their World Cup resolve.
But just as when Stander was sent off against South Africa in 2016, so here too Ireland rode out Aki's red card.
Schmidt's side even stole the bonus-point score before the break, Conor Murray sneaking down a poorly-defended blindside and sending Sexton in for his second try of the night.
Ireland extended that 26-5 interval lead when Larmour crossed on the right flanker, courtesy of more fine work from Murray and Sexton.
TJ Ioane was then sin-binned for repeated Samoan infringement, paving the way for another Ireland score.
Replacement lock Jean Kleyn was denied a try, held up over the line - but on the very next attack his Munster team-mate Stander bulldozed over.
Joey Carbery's smartly stubbed grubber kick let Conway steam home too to seal the victory late on.
Joe Schmidt has admitted he would be "pretty disappointed" if Bundee Aki's red card against Samoa rules him out of the rest of the World Cup.
Ireland thumped Samoa 47-5 in Fukuoka to book their place in the quarter-finals, but Aki was sent off for a high tackle on UJ Seuteni and could now receive a suspension to end his tournament.
New Zealand-born to Samoan parents, Aki was "devastated" by his red card, according to Ireland head coach Schmidt.
Samoa boss Steve Jackson pledged to make whatever representations necessary to help Aki avoid a ban, insisting the red card should prove punishment enough.
Connacht star Aki returned to the pitch at the final whistle, mingling with his close friends in the Samoa line-up - but Ireland boss Schmidt knows that could prove his final appearance of the competition.
"I spoke to Steve Jackson; he's obviously suffered from a couple of red cards or citings from his players in this tournament," said Schmidt.
"It's a really tough situation. Bundee is upright; you can see both his hands behind the shoulder blades of the player who is just starting to come up.
"And it's all split-second stuff. So we live in hope, and we'll see what the judiciary decide.
"But once it's a red card you sense a loss of control over what happens next, no matter what you try to present. We know it's a very hard line.
"I certainly feel for Bundee; he's pretty devastated that any further participation in the tournament is now at risk."
Asked for his take on Jackson's pledge to help Aki avoid suspension, Schmidt continued: "I think Steve was a good player himself, he's coached Super Rugby and for some time, he knows the game well.
"And we'd both be pretty disappointed if Bundee does get ruled out of the rest of the tournament on the back of that tackle. And I do genuinely say tackle, because that's what it was.
"But there is a very hard line being taken and we'll just have to accept whatever decision is made by the judiciary."
Johnny Sexton's two tries spearheaded Ireland's charge to the last eight, with captain Rory Best, Tadhg Furlong, Jordan Larmour, CJ Stander and Andrew Conway also crossing.
Ireland had to battle for almost 50 minutes a man light though, and Aki would be very fortunate not to see his tournament ended by suspension.
Schmidt's men will face either New Zealand or South Africa in the last eight, next weekend in Tokyo. Ireland must wait for the conclusion of Scotland versus Japan on Sunday to discover their opponents.
Samoa boss Jackson made an impassioned defence of Aki's future participation in the World Cup, and will now likely make representations at any World Rugby disciplinary hearing.
"Look, I don't know if I should really comment on it, but there were mitigating factors again," said Jackson, of Aki's red card.
"As you all know it's the toss of a coin at the moment. I think Nic Berry refereed the game very well tonight.
"Bundee is a great character, he doesn't go out there to do that tonight.
"Hopefully the powers that be see some sense and he gets to continue on in the tournament.
"He's a great kid and he deserves it as much as anyone.
"But any contact with the head, people are being penalised. I hope no further sanction comes to him and I hope he can go further in the tournament.
"We'll do everything we can to make sure he gets on the field next week.
"UJ came onto the ball at pace and he only had two or three metres to make the decision on what type of tackle to make.
"That's what's being asked of defenders now. We all know that's extremely difficult, and so we wish him all the best."