For over a century, Galatasaray and Fenerbahce have been battling for football supremacy in Turkey's largest city Istanbul, in the world's only transcontinental derby.
Watched by a voracious media and unforgiving fans, it's a game where losing simply can't be an option.
"It's war," says Yakip Altonisik, a member of Galatasaray's main fan group the UltrAslan. "You can miss out on the title but not the derby."
"The pressure begins at least one month before the match," says Erden Kosova, the co-founder of the Fenerbahce fan club Vamos Bien. "I try and put back the stress until the last minute. But on match day, my head is bursting."
On Sunday, the Yellow Canaries of Fenerbahce, based on the Asian side of Istanbul, will cross the bridge over the Bosphorus to take on the Lions of Galatasaray at their home in the Turk Telekom Arena on the European side of the city in the latest derby.
The rivalry between the two sides is partly determined by geography with fans behaving like an invading navy as they cross the Bosphorus on ferries and chanting.
- 'Collective passion' -
The derby is "remarkable for the magnitude of collective passion that it arouses," says the Turkish writer Tanil Bora, adding the rivalry has been shaped by sociology, philosophy and geography.
When it was founded, Galatasaray was seen as a club of the Westernised Ottoman elite while Fenerbahce was seen as the club of the industrial bourgeois orientated towards Anatolia.
Bora says this translates to two different philosophies that clash -- the intellectual, rational approach of Galatasaray compared with the "aspiration for splendour" of Fenerbahce.
The two teams meanwhile are based around very specific and different areas -- Galatasaray around a francophone lycee in the Beyoglu district of Istanbul while Fenerbache the Saint-Joseph lycee, also French speaking, on the Asian side of the city.
One of the most notorious moments in the history of the derby came in 1996 when Galatasaray's then Scottish manager Graeme Souness planted a club flag in the middle of the Fenerbahce pitch after winning the 1996 Turkish Cup final.
Far from being rebuked by the Gala management, the incident turned Souness into a folk hero for the Galatasaray fans.
- 'In the blood' -
In recent times, Fenerbahce knew its golden age in the 1970s and 1980s. The following decade Galatasaray was the frontrunner, crowned by its victory against Arsenal in the 2000 UEFA Cup, the sole European title won by a Turkish side to this day.
The Istanbul derby has known bloody clashes that sometimes amounted to pitched battles between supporters.
A Fenerbahce fan was stabbed to death after a derby in 2013, an incident that sent shudders through Turkish football.
But since the authorities moved to substantially clean up Turkish football since the 1990s, greater calm has prevailed.
Some supporters, like Erden Kosova, are not overjoyed at the atmosphere in stadiums that are "filled with office workers in shirts who applaud politely". But Turkish stadiums remain among the noisiest in the world.
Turkish football has also changed and Fenerbahce and Galatasaray can no longer assume domination.
Their Istanbul rival Besiktas has revived in recent years, winning the 2015/2016 title while Basaksehir -- formerly the team named after the Istanbul municipality -- has also gained ground.
And this year some would say that the derby is not even a title determining match with Besiktas topping the league and Basaksehir five points behind and Fenerbahce and Galatasaray 11 and 12 points off the the lead respectively.
But the pressure is huge for the players and the staff, with the media stepping up the pressure in the weeks leading up to the match.
"This will be one of the battles that goes down in history," said Fenerbahce's Dutch coach Dick Advocaat.
Tanil Bora argues that in the Byzantine epoch -- before the 1453 conquest of Constantinople -- the great sporting passion was for chariot racing with supporters divided between the Blues and the Greens.
It was fighting between the rival supporters groups that led to the Nika riots against Emperor Justinian in 532 in Constantinople, the worst fighting in its history that razed much of the city to the ground.
This shows, he says, that "this city has the derby in its blood".