FC Cologne's UEFA Europa Conference League opener away at French side OGC Nice on Thursday evening was marred by violent scenes that saw kickoff delayed by 55 minutes.

After visiting Cologne fans were attacked outside the Allianz Riviera stadium, hooligans from both clubs — and others — fought running battles inside the arena, physically coming to blows and hurling objects, including pyrotechnics, at each other.

Local police say that a total of 39 people were injured, including nine police officers and one man who fell from the upper tier, suffering a serious head injury and several broken ribs. Having initially been taken to hospital in a serious condition, the person in question is now conscious and stable.

Meanwhile, some of the approximately 10,000 visiting German fans have been heavily criticized for their behavior in Nice city center during the day, with the city mayor threatening to send a bill to FC Cologne. Conversely, Cologne fans and the club itself have criticized the inadequate policing and security on the Cote d'Azur.

The Group D game in Europe's third-tier competition eventually finished 1-1, a first-half Steffen Tigges opener for Cologne being canceled out by a second-half penalty from Nice's Andy Delort. But all the fallout has focused on events off the pitch.

Questions are once again being raised over the policing of football matches in France after the calamitous Champions League final in Paris in May, but also over the influence of violent hooligan elements in German fan culture, including links between allied fan groups from different football clubs and countries.

What exactly happened and who was involved?

Outside the Allianz Riviera stadium, located 10 kilometers to the west of the city center on the edge of the motorway and the river Var, Cologne fans reported being attacked by local hooligans, with at least one reported to have been stabbed, but not in a life-threatening condition. DW has been told that others wielded sticks, stones and other weapons.

When word of the attacks outside filtered through to fans inside the stadium, where most had been for over an hour before kickoff, approximately 50 of the more violent and hooligan-affiliated elements of Cologne's hardcore ultra groups donned hoods and balaclavas, left the away end and proceeded to cross the main stand in the direction of the main Nice section, lighting and then throwing pyrotechnics as they went.

In a seven-minute long video filmed from the away end, which DW has seen, the Cologne hooligans can be seen accompanied by hooligans and more violently inclined ultras linked to German sides Borussia Dortmund and Rot-Weiss Essen, as well as French side Paris-Saint Germain, with whom some Cologne fans maintain friendly relations.

The PSG ultras from the Supras Auteuil were banned from the Parc des Princes in 2010 under the so-called Plan Leproux, a new security concept introduced ahead of the Qatari takeover of the club, but still regularly attend Cologne games. The game against Nice, with whom the Parisians have their own domestic rivalry, was an added attraction and marked the first time the Supras had officially attended a game in France as a group, with their banner, since their 2010 ban.

Fans familiar with the various fan networks suggested to German broadcaster Sportschau that the fan who was stabbed may have belonged to the Supras, which may have explained the resulting violence inside the arena.

Upon reaching the far end of the stadium, blows and missiles were traded with Nice fans and stewards, before the hooligans retreated, one falling from the upper tier in the process. The man, confirmed to be a French citizen and wearing a balaclava in the blue, red and white colors of PSG, suffered serious head and rib injuries, but is now reported to be in a stable condition.

For their part, Paris Saint-Germain condemned the violence, saying in a statement: "The club reiterates that the group Supras Auteil was dissolved by decree on April 29, 2010, and that its former members are not recognized as supporters of Paris Saint-Germain."

When the Cologne hooligans returned to the away end, video footage showed them being set upon by fellow Cologne fans, calling them "a***holes," asking them "who the f*** are you?" and "what the f*** are you doing?" and chanting "We are Cologne, not you!" Some attempted to remove the hooligans' balaclavas.

Following the hooligans' sortie across the west stand, their French counterparts responded by advancing across the east stand, with scuffles then breaking out in the north-west corner, where police finally intervened.

Despite reports in the French media that the game was set to be abandoned, UEFA ultimately postponed kick-off by 55 minutes until 19:40 local time, on the condition that any further incidents would result in an abandonment.

The game went ahead without further ado, but the fallout has continued.

What have FC Cologne, OGC Nice and the local authorities said?

On Friday morning, local authorities in Nice opened three separate enquiries into events on Thursday, one into "mass violence inside the stadium," a second into "mass violence outside the stadium," and a third into damage caused to the official OGC Nice club shop in city center, where Cologne fans had gathered throughout the day.

Local police commissioner Bernard Gonzalez criticized German fans who had drunk all day for their "inadmissible behavior," while the mayor of Nice, Christian Estrosi, said he was "disgusted."

"It started well but then the degradations worsened as the day went on," he said. "Our trams were graffitied, bus shelters were wrecked, a statue was damaged and there was litter everywhere. The damage hasn't yet been properly assessed but it will be thousands of euros. I'll be sending the bill to Cologne Football Club."

Presented with that assessment, one well-traveled Cologne fan responded: "That's a bit over the top. The city looked like Cologne's old town after carnival. I saw some graffiti and stickers, but nothing massive. It was definitely nothing that should lead to fans being attacked with weapons."

UEFA have also launched disciplinary proceedings against both clubs and German police have set up an investigation, as has FC Cologne, with the club saying it is already in contact with the relevant authorities, UEFA and its organized fan scene.

On Friday morning, Cologne club president Werner Wolf said: "We condemn the horrific scenes that took place before yesterday's game in Nice in the strongest possible manner. We will do everything in our power to clear up what happened and go with full consequence against those who chose violence. We owe that to our thousands of peaceful fans and football in general."

Ahead of kick-off, Cologne captain Jonas Hector had addressed the traveling fans via the stadium PA system, pleading:

"We played our hearts out last season and in the playoffs. We want this game to take place, we want to contest it with you, we want to stand together in peace and as a club. But we don't want to see this and we can't condone it. Please stay calm and support us as best you can."

While traversing the main stand, the hooligans had passed right in front of Cologne head coach Steffen Baumgart, who was in a VIP lounge sitting out a suspension following his red card in the playoff win over Hungarian side FC Fehervar, and who briefly tried to intervene.

"They just looked right through me," he said. "There was nothing I could do. It was pure violence, so we went back into the VIP room for own protection. It's scary when you're right next to it. It will stay with me for a while."

Speaking to local media upon the team's return from Nice, Baumgart continued: "You have to ask how such a situation can come about? Why were the sectors not properly separated? And how can it be possible to enter so easily?"

Having spoken to people present, both German and French, as well as experts in football fan culture, DW can attempt to provide some answers.

French football policing under the spotlight again

Cologne were initially expected to be allocated 1,750 tickets in the north-east corner of the Allianz Riviera, five percent of total capacity in accordance with UEFA regulations. As a result, thousands more fans began buying tickets in the home sections and, given German fans' reputation for traveling in large numbers, Nice expanded the away end to allow around 8,000 fans to sit across the entire north stand. 

Photographs sent to DW suggest that most Cologne fans were in the stadium over one hour before the initially-scheduled kick-off time of 18:45 CET, although many reported that security checks at the turnstiles were inadequate to non-existent.

"We didn't have any problems en route to the ground but we did wonder about the almost complete lack of police presence," one Cologne fan told DW. "The checks at the entrances were only thinly manned, there were far too few stewards and only the odd police officer. Only after the game was there a large police presence."

Furthermore, with the away section expanded well beyond the regular away end in the north-east corner of the stadium, the usual fences and other segregation measures were not present, especially on the western side of the away end, where the Cologne hooligans were easily able to access the main stand.

One source in Nice familiar with French football and the configuration of the Allianz Riviera in particular told DW that the stadium is notoriously badly laid out, with fans easily able to simply walk around the stands and concourses unchecked.

"Nice hooligans were simply allowed to stroll around the entire stadium to the away end, how on earth is that allowed?" asked another Cologne fan. "Then the same scene as on the other side: punch-ups with belts, flares and metal objects thrown. Police? Stewards? Nothing. Why weren't the blocks separated?"

Cologne chief executive Christian Keller insisted that the club had warned the French authorities that a "much greater police presence would have been appropriate," but that such warnings "were not taken seriously or acted upon."

He added: "It was known that there are rival fan groups and it was known that the banned PSG group would probably come and that they have problems with Nice. But our suggestions were generally dismissed."

Following their inadequate handling of the Champions League final in Saint-Denis, just outside Paris, in May, the French authorities were heavily criticized for persistent structural issues regarding the organization and policing of football matches in the country.

"France doesn't have a coherent plan to manage football supporters," Nicolas Hourcade, a sociologist at the École Centrale de Lyon and specialist in French football fan culture, told DW at the time. "There aren't enough stewards, they're not sufficiently trained, and they don't know how to manage crowds of supporters."

Ronan Evain, director of Football Supporters Europe (FSE) and a fan of French side Nantes, called the French policing strategy "repressive," "archaic" and "dictated by a perception no longer rooted in reality."

On Thursday in Nice, the French authorities' decision to allow 8,000 Cologne fans to attend the game in Nice seemed to mark a progressive deviation from the usual policy of issuing a notorious "arrêté préfectoral" — a spontaneous ban on traveling fans often imposed by the local police prefectures on short notice.

Nevertheless, police and stewards still appeared woefully ill-prepared to deal with the influx of fans — especially when confronted with an admittedly extreme level of organized violence. That itself is a reflection of current undercurrents in German fan culture.

Violent undercurrents in German fan culture

In recent years, a clear distinction has emerged in German football between far-right leaning hooligans and generally more left-leaning ultras, with the latter, often supported by the clubs themselves, generally gaining the upper hand.

But now, in some locations, the lines have started to blur, with more hooligan-orientated groups attempting to regain a foothold, including at Cologne and Borussia Dortmund, whose more violent elements maintain amicable links and were partly responsible for the violence in Nice.

"[Generally in Germany,] we can observe a certain part of the spectrum which is more violently inclined and which overlaps with the ultras," explained Hendrik Hübel from the Kölner Fanprojekt, a pedagogical and social work organization that works closely with young football fans in Cologne.

"It's all about power structures. Hooligans can exert influence when certain factors allow them to, for instance, when a club doesn't clearly commit itself to a diverse and anti-discriminatory fan culture, or when hooligan structures are simply so strong that they can just enforce their will by brute force.

"Ultra groups are not all the same," he continued. "Particularly in Cologne, there are many types of groups, and you can see from the images [from Nice] that it's only a tiny fraction which went looking for violent confrontation, and an even smaller fraction which found it."

Following the incidents in Nice, France's minister for sport, Amélie Oudéa-Castéra has demanded "solutions to stop this sort of violence from penetrating our stadiums," while Nice mayor Estrosi has even called for facial recognition for football fans.

"I don't see further restrictive measures like facial recognition or personalized tickets as appropriate means of preventing violence while also allowing fan culture to exist," football social worker Hübel countered.

"The goal is clear: the prevention of violence in stadiums while maintaining a positive, diverse fan culture with all its various facets and avoiding further restrictions for fans. We need to find other ways, such as appropriate security concepts. An effective security concept could have prevented what happened in Nice."

As one Cologne supporter concluded: "It was a complete and utter failure from all involved."

Edited by: Mark Hallam