For the two neighbours challenging for a place in the final of the World Cup, Tuesday’s momentous match does more than cross borders.
Sometimes the frontier between France to the south and Belgium to the north divides the towns themselves in half.
Take the two sister towns of Comines, split in two by accident of history and by a river.
Whether they support Les Bleus to the south or the Red Devils to the north, the residents will apparently have to cheer their teams without the giant screen they have enjoyed during the rest of the competition, for security reasons.
But the mood is still one of friendship, with flags of both nations appearing in the windows of cafes and houses.
The two nations are old footballing rivals, with 73 previous meetings since 1904, three of them in the World Cup.
‘A must-win match’
Belgium is a nation of three languages — French, Dutch and German — but Comines and Comines-Warneton are both French-speaking. So there should be no risk of misunderstandings there.
Although sometimes you wonder.
It may be a game of 90 minutes, but in French the word for 90 depends where you come from. Quatre-vingt-dix in France is widely termed nonante in French-speaking areas of Belgium, as well as in Switzerland.
«This is an absolute must-win for francophone Belgians,» Jean-Michel de Waele from Université libre de Bruxelles told French newspaper JDD.
Belgians, he believes, have an odd love-hate feeling of inferiority. «The Dutch used to be our favourite historic enemy, then France became a footballing nation.»
But what they really cannot bear is French condescension. Don’t ever call them «our Belgian friends» and expect to get away with it.
For most communities straddling the border, spirits are high ahead of Tuesday’s semi-final in St Petersburg.
At another cafe in Comines, La Bascule, barman Bertrand Obert is happy to back both horses: «What’s good about this is that one team or the other will get into the final.»
One French newspaper has billed the match as a duel between friends, summing it up as: «Tintin v Asterix, Abd Al Malik against Stromae, wine versus beer.»
And French sports newspaper L’Equipe channelled its inner Hergé with a front page imitation of the Tintin adventure Destination Moon, promising «the derby of the century».
The mocked-up page shows French coach Didier Deschamps, striker Olivier Giroud and football federation chiefomelu Lukaku heading in a car towards a rocket guarded by Belgian footballers Romelu Lukaku, Kevin De Bruyne and Thibaut Courtois.
The Belgian team is, of course, made up of Flemish and Walloon players, some of whom use English to communicate rather than their native Dutch or French.
Hazard and the French Connection
But then they also have players like Eden Hazard, who hails from the Belgian town of Braine-le Comte but moved to France aged 14 to play for Lille.
Hazard is one of three footballing brothers, and there was delight on French social media when a picture was unearthed of the trio as children in France football strips. paying homage to World Cup-winning striker Zinedine Zidane. Thorgan Hazard, Eden’s brother, is also in the Belgium team.
Justifying his childhood transgression, Eden Hazard said that they had grown up with the 1998 World Cup and at that time there were no Belgium shirts — it was all about Les Bleus.
The French, on the other hand, have Benjamin Pavard, hero of the last-16 game against Argentina. He grew up in the French town of Jeumont, which nestles on the border with Belgium.
Mayor Benjamin Saint-Huile sees the match as a real chance to offer a welcome hand across the border.
«I hope it’ll be a great party and we’ll mix with our neighbours, our friends, our Belgian brothers: it’s an incredible opportunity to make our good-neighbourliness an everyday reality.»
But there is a distinct frisson of rivalry.
Belgium have ex-France World Cup winner Thierry Henry on the bench as assistant to coach Roberto Martínez. And there is clearly a sense of apprehension from his former 1998 team-mate, Didier Deschamps.
«It’s a bit weird because he’s French and he’ll be on the opposite bench. I’m sure it’ll be weird for him too. His playing experience will really help the Belgians,» he said.
The best attacker in French football history would be playing against Les Bleus, complained Le Parisien website, while French TV journalist Gilles Verdez even said he should pull out of the match.
France defender Lucas Hernández was more diplomatic: «Of course he’s working for the Belgians now, but I still reckon he’ll be happy if we win — first and foremost, Henry’s a Frenchman.»