Arsenal2 - 2Bayern

Reuniting seven years from Bayern's third and most recent 5-1 thrashing, the hosts were rewarded for their quick start with a Bukayo Saka strike, but a couple of uncharacteristic defensive mistakes allowed the visitors to turn the tide through Serge Gnabry and Harry Kane's penalty.

However, scintillating substitutes Gabriel Jesus and Trossard combined for the latter to fire home a second-half leveller, but the home crowd were left highly bewildered at full time, as a strong penalty shout for Manuel Neuer's apparent foul on Saka was waved away seconds before the whistle blew.

Boasting a near full-strength squad barring the absence of Jurrien Timber, Arsenal welcomed Gabriel Martinelli and Jakub Kiwior back into their first XI, while a Bayern side led by Kane welcomed back Manuel Neuer and Leroy Sane from injuries.

The faltering German champions - despite the absence of an away support - controlled possession in the opening exchanges, but the first sighter of goal fell to Arsenal's Martinelli in the seventh minute, as the Brazil international fired wide with Neuer rooted to the spot.

Just five minutes later, though, Neuer's dive was futile as Saka opened the scoring for Arsenal in some style, letting a Ben White pass run across his body before a quintessential left-footed curler into the far corner sent the Emirates into pandemonium.

White should have gone from provider to goalscorer in the 16th minute, holding his run and being found by Kai Havertz, but the right-back was not the player Mikel Arteta wanted in that position - he fired straight into Neuer's body with the whole goal to aim at.

The Gunners right-back would be left to rue that wasted chance just two minutes later, as after a cheap giveaway from Arsenal - Kiwior missed Gabriel Magalhaes's pass on the stretch - Sane's ridiculous pass inside found Leon Goretzka, who in turn slipped in ex-Arsenal winger Gnabry to finish under David Raya's body.

Hitherto unbreakable at the back, nerves were evidently setting in for Arsenal's backline, who were carved open once again on the 30-minute mark by a mazy Sane run, and a light clip from William Saliba on the ex-Manchester City man led to referee Glenn Nyberg immediately pointing to the spot.

Arsenal's arch-nemesis Kane inevitably stepped up, and with Raya fatally taking an early step to his right, the England captain had a brief look up and calmly rolled the ball into the opposite corner to turn the first leg on its head.

Carving their way through the hosts' backline like butter on the break, Bayern would seemingly kill the game off in the 36th minute as Sane ran the length of the Arsenal half towards the Gunners' box, but exceptional tracking back from Martin Odegaard thwarted the dangerous German.

With Sane running Kiwior ragged in the opening 45, Arteta threw Oleksandr Zinchenko on for the second half, which began with Arsenal huffing and puffing but failing to make inroads and still looking vulnerable on the counter.

The pace of Tuchel's side continues to pose a world of problems for Arsenal, and one fast-paced break in the 65th minute led to Gnabry having a crack from a tight angle, but his effort was always rising.

Nevertheless, the Bundesliga holders were defending magnificently, restricting the hosts' opening and winning almost every second ball, only to be undone in the 76th minute as Arteta's men drew themselves level.

A lovely flick from Saka into the path of Jesus preceded the Brazil international twisting and turning inside the Bayern box, and the Brazilian's delicate layoff to Trossard - his fellow substitute - infield ended with the Belgian calmly finishing first time into the bottom corner.

There was ample time for extremely close calls in both boxes in the closing stages, as Kingsley Coman's 90th-minute close-range effort fizzed through Raya's legs, but the woodwork saved Arsenal's bacon.

However, it was Neuer who survived the biggest heart-in-mouth moment in the fifth minute of injury time, as the Bayern number one clashed with Saka inside the box after the Arsenal man was released down the right; the contact was undeniably clear, but Nyberg immediately waved away the protests, seemingly believing that Saka had initiated the collision.

The 22-year-old - along with tens of thousands in the crowd - let Nyberg exactly what they made of the decision, and Arsenal assistant Albert Stuivenberg had to put himself in the way of Saka and the referee as the England winger continued ranting and raving.

Prior to next week's mouthwatering Allianz Arena second leg, Arsenal have a tough Premier League home battle with Aston Villa on the menu this Sunday, while Bayern host Koln in Saturday's Bundesliga clash, where their reign of dominance in the German top flight will officially come to an end with defeat.