Gareth Bale and Aaron Ramsey were on the scoresheet as Wales thrashed Republic of Ireland 4-1 in Ryan Giggs' first competitive game in charge.
Tom Lawrence and Connor Roberts were also on target in Thursday's League B Group 4 clash, with Wales totally controlling its opening match in the Nations League.
Martin O'Neill's men were dreadful at Cardiff City Stadium and could have lost by more, Wales easing off after the break having established a 3-0 lead prior to the interval.
But the visitor scored a consolation through substitute Shaun Williams, who capitalised on a Ramsey error to chip Wales goalkeeper Wayne Hennessey.
The host was without a win in eight meetings with Ireland but it led inside six minutes.
Ethan Ampadu's crossfield pass created space on the Wales right, which Joe Allen exploited by sliding Lawrence through on goal, the Derby County man smashing in a near-post finish.
Another diagonal created Wales' superb second 12 minutes later, Ben Davies sweeping the ball out to Bale, who cut inside and curled a brilliant strike into the top-left corner.
Debutant Callum Robinson wasted a good chance for Ireland but Wales extended its lead again in the 37th minute, Ampadu robbing Jonathan Walters and striding forward to feed Ramsey, with his low drive again leaving Darren Randolph beaten at his near post.
Robinson headed a Seamus Coleman centre over the crossbar as Ireland sought a second-half response, but Wales was rampant and added its fourth in the 55th minute.
Lawrence teed up Bale on the left and Wales' star man fizzed the ball across the box, Roberts controlling with his right before lashing home an unstoppable 20-yard volley with his left.
Although Williams made the most of Ramsey's slip a comeback was never on the cards, leaving Giggs to mull over a superb team performance led by Bale and rising star Ampadu.
What does it mean: Ideal start to Giggs era
As a new competition, the Nations League has been met with plenty of confusion, but Wales has taken a commanding position in its section. Ireland, meanwhile, will need positive results in October's double-header if it is to have a chance of topping Group 4.
Pat on the back: Chelsea teenager Ampadu shows passing range
Ampadu was making only his third international appearance but the Chelsea teenager looked at home in a roving midfield role despite typically lining up in defence. The 17-year-old was involved in two goals and looks to have a fine future in Giggs' side, whichever position he plays.
Boot up the backside: Rusty Walters offers no threat
Ireland named a double-pronged attack of Walters and Robinson but the senior strike partner, recently loaned out from Burnley to Ipswich Town, looked well off the pace. He brought a high ball down under no pressure but still tamely surrendered possession to Ampadu, who then created Wales' third.
Key Opta facts:
- Wales picked up its first ever competitive victory against the Republic of Ireland, having failed to win each of the previous four competitive meetings (D2 L2).
- Republic of Ireland has lost back-to-back competitive games for the first time under Martin O’Neill (1-5 v Denmark and 1-4 v Wales).
- Wales scored as many goals in this game as it had in its previous 11 meetings with the Republic of Ireland combined.
- Gareth Bale became the first player to reach 30 goals for the Welsh national team (two more than Ian Rush, 28).
Wales will look to maintain its Nations League momentum when it travels to Denmark - whose senior stars are available after a new commercial deal was reached - on Sunday. A friendly against Poland two days later offers Ireland a chance to rebuild.