Arsenal 3-1 Cologne: Alexis Sanchez and Hector Bellerin rescue Arsene Wenger's side as Gunners start Europa League journey despite delayed kick-off

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Riot police and dog handlers with backs to the game, tasked with controlling the Cologne supporters, might have hoped for a solid Arsenal start to sedate the Germans.

Unfortunately, the security operation is worse on the pitch at the Emirates Stadium than it is off it.

Arsene Wenger's team rarely play with a safety in mind and, true to form, they conceded carelessly, slipped behind and fuelled the bedlam on the wild night of disorder in North London. 

Hector Bellerin sealed the victory for Arsenal when he slid the ball past Cologne goalkeeper Timo Horn

Bellerin roars after scoring Arsenal's third goal of the night against Cologne in the Europa League at the Emirates

Alexis Sanchez rescued Arsenal when he scored with a brilliant right-footed curling effort from inside the Cologne area

Sanchez was quickly followed by his Arsenal team-mates as he ran away to celebrate his side's second goal of the evening

Sanchez then fell to his knees as he celebrated with the Arsenal supporters after turning the scoreline round

They lurched and wobbled to the interval before regaining a grip with the help of an influential change by Wenger and a strong second-half display.

Sead Kolasinac, on at half-time, equalised and Alexis Sanchez fired Arsenal ahead with a delightful curling shot, his first goal since a summer of unrest, to settle the storm and clinch three points in Europa League Group H.

Hector Bellerin added the third in the closing minutes, a deserved goal after a strong display by the right-back, and the early madness was filed away under experience.

David Ospina will be relieved. The goalkeeper sparked trouble when he came wandering out of his goal in a doomed attempt to tidy up an early Cologne attack.

A scuffed clearance landed in a congested midfield and was nudged to Jhon Cordoba who assessed the danger in a flash, swivelled and fired the bouncing ball over the head of his fellow Colombian.

Ospina tried to backpedal but realised he was beaten and dropped helplessly onto his backside as Cordoba's effort nestled into the net.

The Emirates Stadium erupted and the full penetration of Cologne support became abundantly clear.

There were hundreds of them in the top tier of the Clock End and pockets all around the ground, including some of the corporate seats.

Skirmishes broke out as Arsenal supporters took offence as they celebrated and called the away fans be ejected by stewards.

In section where the official away supporters were deployed, they bounced and sang and lit flares as UEFA delegate Roland Tis of Belgium sharpened his pencil.

It promises to be an interesting report and one which does not bode well for Arsenal as they are responsible for the home tickets and the safety of those at the game.

Cologne have been through rough times. They have passionate support and membership went up towards 100,000 as the crashed out of the Bundesliga in 2012.

Goalkeeper David Ospina was punished when he gave the ball away only for it to be fired back past him and into his net

Ospina wasn't able to get back to his goal in time before it gathered in the back of his net in front of the Arsenal fans

Cologne's Jhon Cordoba celebrates his unlikely strike after taking the lead against Arsenal on Thursday evening

Cordoba ran over to the Cologne in celebration as the Arsenal supporters inside the Emirates fell silent

Sead Kolasinac, a half-time substitute, equalised for Arsenal four minutes into the second half with a powerful volley

Kolasinac was mobbed by his Arsenal team-mates after rifling home his strike from just outside the Cologne six-yard area

It was the boost the Arsenal's players needed after a poor first half in which they struggled to break Cologne down

They have been rewarded with an upturn in fortunes under Peter Stoger, finishing fifth last season and back in European competition for the first time since 1992.

Hence the interest and determination to enjoy this night and Arsenal set out as if happy to oblige.

Wenger's team are on UEFA's undercard for the first time since 2000, when they crashed out of the Champions League at the group stage and lost in the final of the UEFA Cup.

They have not started the season in this competition for 20 years and the manager selected his team accordingly.

Seven regular first-teamers were rested with Sunday's game at Chelsea in mind but was able to select a familiar front-three of Sanchez, Olivier Giroud and Theo Walcott.

Giroud saw one header saved by Timo Horn and another slide a couple of yards wide from a Sanchez cross. Walcott dragged a sharp chance wide, while under pressure but the Londoners lacked composure in a frenzied first-half.

Midfielder Jack Wilshere made his return for Arsenal from the substitutes' bench as he came on for Alex Iwobi

The Cologne supporters produced plenty of noise with many of them in different sections of the stadium

Cologne supporters set off flares during the Europa League group stage match against Arsenal on Thursday

Their instinct was to pour forward but Cologne dropped deeper and sought to punch on the counter-attack but Wenger settled minds during the half-time break.

Within four minutes of his introduction, Kolasinac had lashed a volley past Horn from an angle after Walcott's burst into the penalty area and the momentum changed.

Arsenal started to perform with purpose with Sanchez pushed further forward by the change of formation from a back-three to four.

Iwobi flashed one over and Ainsley Maitland-Niles carved into the box only for Horn to slide out and save at his feet.

Sanchez cut in from the left and curled in the second. 'In second half he came alive,' said Wenger. 'He is fighting to get back to his best physically but Sanchez is an exceptional footballer and he can still deliver the decisive pass or goal.'

Bellerin stabbed in the third. It did not exactly silence the Germans. The volume may have gone down a notch but, by the final whistle, they were the only supporters left inside the stadium.

The Europa League match between Arsenal and Cologne was delayed by an hour following crowd trouble 

Cologne supporters were stopped on a walkway as they tried to get to the Emirates hours before kick-off

Riot police moved into the section where the away fans had been housed after fights broke out

Riot police stayed in place throughout the match in an effort to prevent any further outbreaks of trouble happening