World No. 1-ranked Ireland announced itself in dominant style at the 2019 Rugby World Cup with a bruising 27-3 win over Scotland on Sunday.

Ireland, which has never gone past the quarterfinals of the tournament but is considered a serious contender to lift the trophy this year in Japan, bulldozed through the Scots with three first-half tries at Yokohama International Stadium, all scored by forwards.

A second-half downpour did little to silence the sea of green-clad Irish fans among the crowd of 63,731, and Andrew Conway gave them more to sing about when he scored in the 56th minute to secure a bonus point for his team.

Ireland has beaten New Zealand twice in the last three years and won the Six Nations three times since 2014, and head coach Joe Schmidt was pleased with the way his team got its quest to land rugby's ultimate prize under way.

"I was delighted with all 23 (players)," said Schmidt, whose team plays Japan in its next game in Shizuoka on Sept. 28. "I think one of the things that sometimes happens is you build a lead and then you lose a little bit of cohesion when guys start filtering in and out. I didn't really detect that that happened. The conditions made it really difficult for us to construct things but we scored a try in the second half when those replacements were on.

"That was really pleasing, but also that front foot that we got off to. It takes a little bit of pressure off in the game. It means they have to chase it a little bit, they have to take a few more risks than we do. And at the same time, I was happy with the risks that we did take."

The Scots, meanwhile, struggled to gain any kind of foothold, with a lone Greig Laidlaw penalty giving them their only the points of the game.

Scotland now heads to Kobe to take on Samoa in its next match on Sept. 30, and head coach Gregor Townsend knows there is no margin for error with Russia and host nation Japan also lying in wait.

"Disappointing, is the initial thought," he said. "We didn't start with the energy, accuracy and aggression that is required to beat a team like Ireland. Ireland started very well and they took their chances when they got into our 22. And probably of any team in world rugby, if you give them a 15-to-20-point start, it's going to be very difficult to come back.

"We need to win our next three games. We have to bounce back and play a lot better against Samoa and carry that on to Russia and especially Japan, who have started well."

Ireland imposed itself on the game early, and after camping out on the Scottish goal line, James Ryan bludgeoned his way over in the sixth minute to touch down for a try which Jonny Sexton converted.

Ireland's second score, eight minutes later, was just as physical. This time the Irish forwards drove through the Scottish defense over by the left touchline, and captain Rory Best finished the move off in the corner. Sexton, however, could not add the conversion.

Laidlaw kicked a penalty to put Scotland on the scoreboard, but Tadhg Furlong rumbled over minutes later to notch Ireland's third try and this time Sexton made his kick.

Pouring rain throughout the second half complicated Scotland's efforts to get back into the match, with one pass slipping through standoff Finn Russell's fingers with the Scots in a good position to attack.

And Conway put Scotland in a deeper hole when the Irish winger scored a try midway through the second half, bouncing off tackles before diving over in the corner.

A Jack Carty penalty widened Ireland's lead, and Scotland failed to add any more points before the final whistle as the Irish defense stood rock solid.

"It was a good start for us," said Best. "When you start the tournament against a team like Scotland, you have a lot of nerves. You know you have to play well, you know you have to start well. I think for us, from a forward's point of view, to get a couple of tries is pleasing. But I think we know that it's just the start and we need to get better."