Crowd disorder marred Cologne’s return to European competition after 25 years as the German team’s fans caused havoc in London and forced the Europa League game against Arsenal to be delayed on Thursday.Arsenal manager Arsene Wenger was surprised that the game was eventually played after a one-hour delay, with his team winning 3-1.The presence of thousands of ticketless Cologne fans, who marched through the streets of the British capital, made it hard for ticketholders to enter the Emirates Stadium.Police said four people were arrested for public order offenses. About 20,000 Cologne fans came to London, after only 3,000 tickets were allocated to them.?? #ElNinoMaravilla#AFCvCOL pic.twitter.com/zswK61ihGS- Arsenal FC (@Arsenal) 14 September 2017″At some stage I thought they would not play the game, because I can’t see the police taking any risk,” Wenger said. “We live in a society of 100 percent security and I thought they would never take a gamble to play this game when I saw the images around the stadium. But I must say our supporters as well dealt well with the situation as well and there was no aggravation.”Great response from everyone after a difficult start in the @EuropaLeague! On to Sunday now. #COYG pic.twitter.com/khijIW7kfU- Hctor Bellern (@HectorBellerin) 14 September 2017Wenger said Cologne supporters had been “very clever” to enter the stadium undetected.”I don’t know how they managed to infiltrate our fans and get everywhere but they did that very well,” he said. “I don’t know if they went through Arsenal membership, on the internet … they did very well.”advertisementCologne coach Peter Stoger declined to be questioned on the actions of the supporters.”I have no comment about the fans,” he said. “I’m the coach. My job is the team. My job is football not the fans.”Good to start with 3 points, but also respect for the performance of @fckoeln????? #COYG #UEL @Arsenal- Mesut ?zil (@MesutOzil1088) 14 September 2017Cologne sits winless on the bottom of the Bundesliga, but its fans – walled off by security guards in the stadium were celebrating after only nine minutes when Jhon Cordoba lobbed goalkeeper David Ospina from 40 yards out.Not a bad way to score your first goal at the Emirates…?? @seadk6 pic.twitter.com/4ZiAcHFuPS- Arsenal FC (@Arsenal) 15 September 2017It took Arsenal 40 minutes to reply, through substitute Sead Kolasinac. Alexis Sanchez hit the match-winner, and started the move for the last goal, a rebound effort finished by Hector Bellerin as Arsenal won a Group H match that is likely to lead to UEFA charges over the disorder.