Arsenal have one foot in the last four of the Europa League after producing a scintillating attacking display against CSKA Moscow in the first leg of their quarter final tie.
Arsenal made five changes from Sunday's win over Stoke, two of them enforced. David Ospina picked up an injury against the Potters so Petr Cech came in for a rare Europa League start. Pierre-Emerick Aubameyang was cup tied, with Alexandre Lacazette replacing him up front. CSKA fielded the same goalkeeper and back three as their last visit to Arsenal 12 years ago.
The Gunners nearly produced a goal within the opening five minutes as good work from Aaron Ramsey and Mesut Ozil released Mkhitaryan, but the Armenian's shot could only ripple the side-netting. Ahmed Musa was then denied a clear run at Cech's goal by an erroneous offside flag.
The flag was up again soon after, this time against Arsenal, as a fine Ramsey finish was ruled out for a marginal offside decision against Ozil. But they weren't denied for long - another flowing move from the hosts culminated in a clever Bellerin pass which found Ramsey in space, and the Welshman made no mistake with his finish.
Arsenal looked like they could score every time they went forwards, but their defensive vulnerabilities cost them yet again. Shkodran Mustafi and Granit Xhaka fluffed their clearances before Laurent Koscielny gave away a silly foul. Aleksandr Golovin stepped up and curled a brilliant free kick past Cech to bring the Russians level.
Musa then worked some space in the Arsenal box from CSKA's very next attack, and only lacklustre finishing saved the Gunners from going behind. But they were back in front when Ozil was fouled in the box by Georgi Schennikov, and Lacazette sent Igor Akinfeev the wrong way from the spot.
And in the blink of an eye, it was 3-1. Ramsey beat the offside trap to get on the end of a dinked cross from Ozil, and he produced a brilliant finish with the outside of his right boot to loft the ball over Akinfeev. CSKA nearly fashioned an immediate response but Vasili Berezutski blazed into the crowd after a good run from Musa.
Every Arsenal attack was an exhibition in quick passing and movement which CSKA's ageing back line couldn't cope with. Ozil was again the creator, collecting the ball on the edge of the box before picking out Lacazette in the middle. The Frenchman took one touch before finding the bottom corner of the net to make it four.
CSKA also looked dangerous in attack but lacked Arsenal's killer touch, with Alan Dzagoev skying two chances over the bar in quick succession. Musa then raced forwards with intent but struck a tame shot when a pass to Schennikov would have been a better option.
Ozil should have added a goal to his two assists as he got on the end of a Xhaka cross but failed to test Akinfeev. There was no added time at the end of the half, and the Emirates rose for a rare standing ovation in honour of a devastating first 45 minutes.
Arsenal picked up where they left off after half-time and only a last ditch block from Sergei Ignashevich denied Ramsey his hat-trick. He then blasted over another chance after Akinfeev had pushed away a Mkhitaryan shot.
CSKA thought they were back in the tie when Pontus Wernbloom's shot was parried by Cech and Dzagoev headed in the rebound, but again they were denied by the linesman's flag - correctly on this occasion.
Arsenal should have had five as a presentable opportunity fell to Alex Iwobi, but he inexplicably chose to pass instead of shooting and the chance went begging. The Nigerian nearly redeemed himself with an assist for Ozil, but Akinfeev kept it out and Ramsey was offside on the follow up.
The Welshman was still desperately seeking his third goal and went within a few inches of getting it as he sidefooted against the post from just inside the area. Substitute Danny Welbeck then tested Akinfeev from point-blank range but the 31-year-old proved equal to it. Ramsey scuffed yet another shot wide as Arsenal sought that elusive fifth goal.
They didn't get it, but Arsene Wenger will be very happy with the first half display and a result which puts the Gunners within touching distance of their first European semi final since 2008-09. The second leg is next Thursday at the VEB Arena.