Match ends, Arsenal 3, Dundalk 0.
Arsenal's squad players impressed boss Mikel Arteta as they eventually broke Dundalk's resistance to win their Europa League group game at Emirates Stadium.
Eddie Nketiah pounced from close range to give the Gunners the lead and Joe Willock blasted a shot into the roof of the net 125 seconds later.
Nicolas Pepe's brilliant effort from the edge of the box seconds after the restart killed the game off.
They cruised after that but could not add a fourth against the Irish side.
"We gave a chance to a lot of players who haven't played many minutes this season and it is something really positive because they showed they are well-prepared, they are at it, and they are ready when we need them," Arteta said.
"They are always in the frame to play. It is not if we lose or win, it is what they bring to the team."
It was a stark contrast to Spurs boss Jose Mourinho's criticism of his fringe players as Arsenal's north London rivals lost 1-0 to Royal Antwerp.
Arsenal - who had never faced a side from the Republic of Ireland before - have now won both their opening Europa League games, while Dundalk have lost both of theirs.
Dundalk made a bit of history as the first team in the 10 years of the Europa League not to commit a single foul in a game.
Gunners' inexperienced backline not tested
Arsenal handed a debut to Iceland goalkeeper Runar Alex Runarsson, a summer signing from Dijon, and he played behind a makeshift central defence.
The Gunners have three centre-backs injured, including David Luiz, with another two not registered for the Europa League.
As a result Shkodran Mustafi, making his first start since July, began in a back three along with midfielder Granit Xhaka and Sead Kolasinac, who is usually a left-back but has played in the centre for Arsenal several times.
But they all had a quiet day - Dundalk only had two touches in Arsenal's box - and it was the hosts' fringe forwards who took their chance.
It took 33 minutes for the Gunners to have a shot on target, with Kolasinac's header tipped over the bar by Gary Rogers.
The breakthrough came seven minutes later. Rogers flapped at a corner which hit team-mate Daniel Cleary and Nketiah beat Brian Gartland to the loose ball to score from close range.
Two minutes later and the Gunners had control. A misplaced pass let Nketiah run forward. He found Pepe, who had an effort blocked, but Willock controlled the ball and blasted a shot into the roof of the net.
It was only another couple of minutes of football later - albeit after the half-time break - when the best goal of the day came.
Pepe got the ball on the edge of the box, rolled it away from a defender and smashed a perfect effort into the top corner.
At that stage a rout looked likely but Dundalk held firm with Ainsley Maitland-Niles having the only effort on target after that.
Arteta said: "I'm really pleased with the way we went about the game.
"Our attitude from the beginning was spot on, we attacked and created a lot of situations inside the box."
Dundalk deserve credit
Dundalk's run to the Europa League group stage has come despite domestic struggles. They have won only three of 11 League of Ireland games since the restart, losing their title to Shamrock Rovers, and are not certain of a European place next year.
Their manager is unknown Italian Filippo Giovagnoli, a former AC Milan summer camp coach who had never managed a senior team until his appointment in August.
He was not expected to be in the dugout - he sat out their 2-1 defeat by Molde last week - because he does not have the Uefa Pro Licence.
Shane Keegan, the club's opposition analyst, was named as manager for the game in the Uefa team sheet - but Giovagnoli appeared on the touchline for the game.
They had the opening chance with Patrick McEleney's long-range effort after three minutes tipped around the post by Runarsson.
The Lilywhites defended resolutely for 40 minutes but Arsenal's opening two goals came from their mistakes and there was no way back after that.
Giovagnoli said: "I want to congratulate my team and all the players for the way they collaborated defensively, their focus and everything.
"We had to suffer, we know, but I think we were organised defensively.
"A few things went well, we tried on three occasions to build up like we prepared, we tried to high press them when they were playing with the goalie, to go man to man and be really aggressive when their goalie had the ball."
Several players were withdrawn with Sunday's league game against St Patrick's Athletic in mind. Among them were Michael Duffy, who is such a big Arsenal fan he took 'Thierry' as his Confirmation name after Gunners legend Henry.
Limerick's 1-1 Uefa Cup draw in Southampton in 1981 remains the only time in 13 attempts a side from the Republic of Ireland have not lost in England.
Nketiah scores, Arsenal win - match stats
- Arsenal have lost just one of their 13 games in cup competitions under Mikel Arteta (W10 D2), a 2-1 defeat against Olympiakos in February.
- Arsenal have won all nine games in which Eddie Nketiah has found the back of the net (10 goals).
- Goalkeeper Runar Alex Runarsson is the first Icelandic player to appear for Arsenal since Olafur Ingi Skulason against Wolves in December 2003 in the League Cup.
- 20MustafiSubstituted forCeballosat 61'minutes
- 34XhakaSubstituted forTierneyat 74'minutes
- 17Cédric Soares
- 19PépéSubstituted forWillianat 62'minutes
- 30NketiahSubstituted forBalogunat 74'minutes
- 21ClearySubstituted forHoareat 53'minutes
- 16MurraySubstituted forSloggettat 45'minutes
- 5ShieldsSubstituted forGannonat 62'minutes
- 11McEleneySubstituted forFloresat 53'minutes
- 7DuffySubstituted forColovicat 70'minutes
- Filip Glova
- Shots on Target
Second Half ends, Arsenal 3, Dundalk 0.
Attempt missed. Mohamed Elneny (Arsenal) right footed shot from outside the box is too high. Assisted by Dani Ceballos following a corner.
Attempt blocked. Kieran Tierney (Arsenal) left footed shot from the left side of the box is blocked.
Corner, Arsenal. Conceded by Brian Gartland.
Foul by Dani Ceballos (Arsenal).
John Mountney (Dundalk) wins a free kick in the defensive half.
Attempt missed. Reiss Nelson (Arsenal) right footed shot from outside the box misses to the right. Assisted by Dani Ceballos following a corner.
Corner, Arsenal. Conceded by Stefan Colovic.
Corner, Arsenal. Conceded by Andrew Boyle.
Foul by Reiss Nelson (Arsenal).
John Mountney (Dundalk) wins a free kick on the right wing.
Corner, Arsenal. Conceded by Jordan Michael Flores.
Attempt missed. Kieran Tierney (Arsenal) left footed shot from the left side of the box is too high. Assisted by Reiss Nelson.
Foul by Joseph Willock (Arsenal).
John Mountney (Dundalk) wins a free kick in the defensive half.
Attempt missed. Patrick James Hoban (Dundalk) right footed shot from outside the box is high and wide to the left from a direct free kick.
Foul by Willian (Arsenal).
John Mountney (Dundalk) wins a free kick in the attacking half.
Substitution, Arsenal. Folarin Balogun replaces Eddie Nketiah.
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