Arsenal were not happy with referee Mike Dean over Koscielny’s dismissal and City even less so when with 15 minutes left captain Vincent Kompany was sent-off for a challenge on Jack Wilshere deemed dangerous by the match official.
Less than ten minutes had elapsed when Arsenal hit the self-destruct button. Gareth Barry’s looping header back into the home side’s box saw Dzeko turn Koscielny, who reacted to the danger with a challenge agricultural to the extent that it was met with a red card and penalty award.
Dzeko stepped up but saw his spot-kick strike Wojciech Szczesny’s outstretched legs before coming back off the far post and rolling into the arms of Arsenal’s relieved goalkeeper.
It was a reprieve that was to prove only temporary as City forged ahead on 20 minutes when from a quick free-kick Arsenal were again caught napping. After the ball was worked to Carlos Tevez his cute slide-rule pass was dispatched with venom and accuracy courtesy of James Milner’s angled drive from around 12 yards.
With ten-man Arsenal looking disjointed and on the ropes City went for the jugular and delivered the knock-out blow of a second goal just five minutes later. Trademark Pablo Zabaleta appetite for the fight brushed an insipid Kieran Gibbs off the ball before he set Milner on his way down the right. Tevez’s prod for goal from his team-mate’s low delivery forced Szczesny into a save but he could only parry straight into the feet of Dzeko no more than a yard out.
Thereafter the rest of the first half proved to be the proverbial stroll in the park for City as only Wilshere’s presence on the goal-line prevented Javi Garcia from adding a headed third from Milner’s corner.
After the interval Arsenal at least dug a little deeper but still it was City who conjured the first real opportunity when Milner stood one up at the back post only for Dzeko to head over.
Wilshere drove the play forward wherever possible and it was from one of his bursting runs that Gibbs saw his drive from the edge of the box blocked by the industrious Milner.
Referee Dean was busier than either goalkeeper though for the most part of an ill-tempered rather than malicious contest that saw Thomas Vermaelen, Milner, Wilshere, Gael Clichy, Bacary Sagna, Garcia and Gareth Barry all pick up bookings.
With 20 minutes remaining and City content to hit Arsenal on the counter-attack, Tevez was guilty of profligacy when after he was played through by Dzeko an over-elaborate attempt to round Szczesny allowed the keeper to save.
Substitute Olivier Giroud will be disappointed with a headed effort wide from a set-piece but it will be Kompany’s red card that will be given more column inches. The Belgian’s tackle on Wilshere looked to take the ball but Dean ruled it to be two-footed and dangerous.
City spent the remainder of the contest largely on the back foot but for the most part Arsenal were restricted to no more than half chances, with substitute Joleon Lescott earning his win bonus when clearing Theo Walcott’s late effort off the line in a rare moment of genuine danger.
Roberto Mancini’s side kept their heads though to stay within seven points of neighbours and league leaders Manchester United.