IT HAS become a familiar ritual. A drum beats twice. A wall of blue-shirted fans grunts and lets rip a thundering clap. The pace quickens, like a Viking horde charging into battle. After every victory—and there have been many in recent years—Iceland’s football players and fans unite in performing the clap, which has become one of the sport’s most loved traditions. Last month it boomed out once again. After a 2-0 win against Kosovo on October 9th, Iceland, with a population of just 330,000 and a manager who doubles as a part-time dentist, became the smallest ever country to reach the 32-team finals of the men’s World Cup. They will be one of 14 European sides to compete in the 21st edition, hosted by Russia next year. “It means the world,” says Gudni Bergsson, a former national captain who is now president of the Icelandic Football Association. “For years we have watched the major tournaments on television. People would choose their sides and which countries to support. Now we are actually going there.”

To the outside world, strakarnir okkar (“our boys”) must seem like the most improbable qualifiers in World Cup history. The sparsely-inhabited volcanic territory is home to a quarter as many people as Trinidad and Tobago, which previously held the record for the puniest finalist. Of the 54 European countries to have entered this year’s qualifiers, only five are smaller: Gibraltar, Liechtenstein, the Faroe Islands, Andorra and San Marino. Together, they scored just 12 goals between them in their 50 games while conceding 176. Nor can Iceland boast a long history of footballing prowess. Six years ago they were ranked outside the top 100 sides by the World Football Elo Ratings, which uses the Elo formula and is a better predictor of match outcomes than the official rankings published by FIFA, football’s global governing body.

In the ensuing years, a cohort of young Icelandic men reached the under-21 European Championships for the first time in 2011, came within a game of qualifying for the last World Cup in 2014 and finally made it to a major senior competition at last year’s European Championship, when they reached the quarter-finals and knocked out England. The women’s team has also qualified for the last three editions. Today the Elo system ranks the men 19th in the world. That makes them good enough to warrant their place in Russia, but by no means a shoo-in. The Netherlands, who are ranked 11th and have reached the semi-finals in the last two World Cups, will watch next year’s tournament from the sidelines. To secure automatic qualification Iceland had to beat Croatia, Ukraine and Turkey, each of whom has been a World Cup quarter-finalist in the last 20 years. How did a country with such a tiny player pool and barely four hours of daylight in its brutally long winters produce a team of world-beaters?

In the late 1990s, the Iceland Football Association (KSI) began to recognise that hostile weather was holding back its 50 or so clubs. So in 2000 it opened the country’s first indoor football facility, complete with a full-sized pitch and a dome; today there are seven such outfits. In 2003 UEFA, European football’s governing body, launched HatTrick, a funding programme for grass-roots development, which helped Iceland to build more than 100 all-weather artificial surfaces for schools. Though these are outdoors, most have floodlights and all have under-floor heating.

But footballers cannot thrive on pitches alone. Fortunately, this construction work was accompanied by a coaching revolution. In 2003, not a single Icelander had a UEFA A- or B-level coaching qualification. Now around 800 do. All footballers from the age of four are taught by such instructors. This scheme has yielded a handful of players who combine the tenacity that was the country’s historical hallmark with intricate skill, most notably Gylfi Sigurðsson, who transferred to Everton for £45m ($60m) this summer. All 25 members of the current squad play for a foreign club, with six in Britain and two in Germany.

Nonetheless, uniquely among the European countries to have qualified for the World Cup, no Icelanders are taking part in this year’s Champions League, Europe’s premier knockout competition. Despite the country’s admirable facilities and coaching, the team has had to compensate for a lack of talent on the pitch. Heimir Hallgrimsson, the dentist-cum-manager, calls his players “workaholics”. Match statistics for international fixtures are surprisingly scarce—we could only find reliable records for competitive European games in the last eight years—but the data that we gathered suggest that Iceland have adopted guerrilla tactics with startling effectiveness.

Of the 53 teams to have contested at least 30 games in our sample, the Nordic side ranked 40th in terms of the average share of possession that they obtained in their matches. Allowing the opposition to dictate the play is usually a recipe for disaster. Five-sixths of the variance in points earned by European international teams in this period can be explained by their possession, so strong is the relationship between the two. Iceland’s 46.9% portion of time spent with the ball would typically yield 1.1 points per game—barely half what is needed to challenge for World Cup qualification. The same is true when looking at the number of chances a team creates and concedes. The Nordic side typically took 2.6 fewer shots than their opponents, which should also have earned them 1.1 points on average. Yet they have collected 1.5 points per game across their 47 fixtures in our sample, exceeding their projected total by a greater proportion than any other country. Their success in the current World Cup campaign has been even starker, converting just 41.6% possession into 2.2 points per match, and collecting a miraculous ticket to Russia.

Such a degree of overachievement relative to possession has two possible explanations. The first is that Iceland have genuinely figured out how to consistently manufacture better scoring chances than their opponents while mounting a rearguard defensive operation. That strategy has been perfected by Atlético Madrid, who have had less than 50% possession and earned at least two points per match in each of their last five seasons. In that time they have reached two Champions League finals and won La Liga, wrenching the title from Barcelona and Real Madrid for the first time in a decade. Atlético’s regular heists are no fluke. Expected goals, a statistic which measures the quality of shooting chances, suggests that they typically create a surplus of likely scoring opportunities in their games, despite their defensive emphasis. For the second potential cause of Iceland’s improbable success, look to the only other team in a major European league in the last five years that has had less than half of possession and won more than two points per game: the fabled Leicester City side that won the Premier League in 2016. The Foxes’ glory was largely caused by a hot streak in front of goal and wasteful opponents. Their final goal difference of 32 was nearly twice what the quality of the chances in their games would predict, and they allowed as many shots as they took. You can ride your fortune for a while, but not forever. In their subsequent season they fell to 12th place, which was still their second-best performance since 2000 but not enough for Claudio Ranieri, their eccentric manager, to keep his job.

The data for international matches are too meagre to tell us how good Iceland’s opportunities have been, and therefore how sustainable their success might be—though they created a surplus of 2.7 shots per game in their World Cup qualifying campaign, suggesting that their recent triumphs have been more like Atlético’s than Leicester’s. Whatever the cause, the fans hope that it will continue for their three pool games (and any subsequent knockout ties) next summer. Last June about a tenth of the entire country journeyed to France for the European Championship. At times the vociferous travelling crowd made foreign stadia feel like Laugardalsvöllur in Reykjavik, where Iceland have not lost a competitive game in four years. Thousands will now be planning their trips to Russia for the World Cup, in expectation of more shocks and thunderclaps. And those who run football in Iceland are already plotting how to use the exposure and extra cash from qualifying. “We can attract more attention to Icelandic football, both financially and professionally,” says Mr Bergsson. “We will be in an even better position to continue to work with the clubs in Iceland to help them produce quality players, both men and women. That way, we can hopefully prove again to all that getting to the Euros and the World Cup were not flukes.”