But it was not to be as substitutes Aaron Ramsey and Giroud struck late on to seal a remarkable three points for Wenger's side.
2nd min (GOAL) - A dream debut for Lacazette as the £52million summer signing headed in an elegant opener.
Leicester showed some of the form that won them the title in 2016 and helped stave off relegation last term but in the end they were undone by canny France worldwide Giroud who has been linked with a move away from Arsenal all summer.
One new recruit, defender Harry Maguire, felt Leicester gave the hosts a run for their money and - despite heading back to the east midlands with nothing to show for it - believes the display will hold them in good stead.More news: Scaramucci: Trump Charlottesville Statement Should Have Been 'Much Harsher' on White Supremacists
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From Hector Bellerin's lay-off, Mohamed Elneny swept a first-time cross into the box and Lacazette deftly glanced a header past Kasper Schmeichel before spreading his arms to take the acclaim of the crowd.
It seemed an unlikely platform for victory, but Ramsey neatly controlled Xhaka's dinked pass to drill in an equalizer and moments later Giroud's header from Xhaka's corner completed a remarkable turnaround. And once again, Arsenal were statuesque at a set piece, allowing Vardy to bustle to the front post and head past Petr Cech.
A loose ball from Granit Xhaka found its way to Marc Albrighton, who guided a magnificent cross into the penalty area from the left flank.
Over the years, we've seen a clear pattern of how Arsenal's seasons usually plan out, and they should look to distinguish that this season.
Leicester then broke the tie in the 29th minute as top scorer from Leicester's Premier League winning season, Jamie Vardy opened his 2017-18 account with a stunning volley with his left foot. Mahrez whipped in a delightful corner and without any real aerial presence, Vardy rose highest to apply the finish.
'Defences are terrified of his pace which is fantastic for us as we have him on our side and we can utilise it as much as possible. "It looks like everywhere there is many, many players and a bit of congestion at the moment everywhere".