There’s a first time for everything. The Football League in England was founded in 1888, and since its inception there has never been a matchup in the top flight between two clubs from Wales. There are nine Welsh clubs competing in the English football league system and only two have ever won a major honor in England: Cardiff City (1927 FA Cup) and Swansea City (2013 League Cup). It just so happens that both those clubs are from South Wales and have one of the nastiest rivalries in the sport.

There are many derbies of varying intensity throughout the world of football: El Clasico in Spain, Superclasico in South America, Liverpool-Manchester United in England, Derby della Madonnina (the Milan Derby) in Italy, The Kitalar Arasi Derbi (between Fenerbache and Galatasary) in Turkey and The Old Firm in Scotland, to name a few of the more volatile matchups. Most derbies are a result of extreme geographical, political, and/or religious differences. For American sports fans, the power of these derbies can’t be explained by saying “It’s like the Red Sox versus the Yankees or North Carolina versus Duke” because they simply don’t compare when it comes to the air of menace and the level of hatred involved with these derbies.

The South Wales Derby is a footballing war that (for the most part) has gone largely unseen by anyone outside of Wales. Now, with the global reach of the Premier League, this derby will take center stage on Sunday in front of a potential worldwide audience of over 700 million people across 212 territories.

The first match between the two took place 101 years ago. For the better part of fifty years, there appeared to be no tribalism between supporters of the clubs. But that may have changed starting in 1955 when Cardiff was selected as the capital city of Wales. What provoked the citizens of Swansea was not so much that Cardiff had been named ‘capital,’  it had more to do with the feeling that the Welsh  government had begun to finance the city of Cardiff, while ignoring Swansea which was only 30 miles down the coast. Many citizens of Swansea still feel that they are ignored by the Welsh government as new monies are continually sent to Cardiff.

Things between the clubs seemed to escalate during a quarter-final matchup in the 1960 Welsh Cup when tension between the club directors spilled out on to the pitch. Those who recall the match described it as “brawl more than a football match”.

Much like some English derbies, the South Wales Derby turned its ugliest during the 70’s and 80’s when ‘football hooliganism’ was at its peak.

Swansea supporters continue to celebrate their most “famous” off the field victory over Cardiff by singing ‘Swim Away’ in honor of one particular clash. The ‘Swim Away’ chant (accompanied by breast stroke actions) derives from a 1988 encounter. Following a defeat to the Bluebirds, the Swansea fans hunted down some of Cardiff’s fans and chased them towards the beach until the Cardiff fans attempted to escape the Jack Army by diving into the bay. By attempting to swim away from the Swansea fans, those Bluebird supporters brought a new emphasis to the Jack’s rendition of ‘Swim Away’. Since then, the ‘Swim Away’ chant regularly resonates from the Jack Army in a taunt at Cardiff fans.

‘The Battle of Ninian Park” took place in 1993 and made headlines across Europe. A comparatively quiet match buildup was marred by crowd violence after the arrival of 1,000 Swansea fans caused the kick-off to be delayed. Hooligans made their way on to the pitch from the grandstand and seats were torn out and hurled at rival supporters shortly after Cardiff scored to take the lead. Many feel that this match brought a tremendous amount of shame to Welsh football.

This kind of fan violence is now a small element of the South Wales Derby. It is really only reserved for a minority of die-hard supporters on each side. But players from both sides have been known to get involved in the taunting of opposing supporters.

In 2006, during Swansea’s LDV Vans Trophy final victory over Carlisle at Cardiff’s Millennium Stadium, Swansea’s Lee Trundle and Alan Tate displayed a Welsh flag they retrieved from the crowd which had the words “F**k off Cardiff” written across it.

The players should be leery of getting involved with antics such as this. This week, the Daily Mirror relayed the story of Andy Legg who played for both Welsh clubs. Legg described receiving numerous death threats in the mail and also recounted a story of one his teammates, Winston Faerber, who had accidentally opened some of his mail:

‘Winston opened one of my envelopes and there was half a razor blade fitted into it,’ Legg said. ‘I’d had some death threats before, but this was pretty nasty.

‘It sliced right into his finger when he opened it. I got a lot of abuse in that initial time after joining, some from Swansea fans unhappy that I left and some from Cardiff unhappy that I was a Jack.

“Frank Burrows, our manager at Cardiff, always used to say, ‘If you can’t take the abuse you shouldn’t be in football.’ I agree with that, but it’s a pretty big rivalry, that one [South Wales Derby]. Oh my God, it’s a big one.”

As both clubs moved into new stadiums and police presence increased, the number of violent incidents has greatly decreased. What remains is the passionate banter between the two supporters groups that will make for an intense atmosphere come kick-off time in Cardiff.

Annis Abraham is a reformed hooligan who was part of Cardiff’s notorious Soul Crew firm in the 1980s. Recently, the Guardian newspaper quoted this Cardiff season ticket holder of 41 years: “We haven’t walked the streets of each other’s ground for 15 years. People say the police are ruining it; they’re not. I don’t stick up for the police usually but they’re preventing a bloodbath. As much as I detest the way they’re brought in at Cardiff and we’re brought in at Swansea, it is needed.”

It could be argued that for the first time going into a derby since 1998, Swansea is playing to retain bragging rights as Wales’ top club. The Swans are competing in Europe (the Europa League), coming off a Capital One Cup victory (2013), and has been in the Premier League since 2011.

Cardiff has won the Welsh Cup twenty-two times and finished runners-up an additional six times. While Swansea has taken home the silverware ten times and been named runners-up eight times.

Cardiff holds the lead in 105 competitive head-to-head matches. The Bluebirds have beaten the Swans 43 times, drawn 27, and lost 35. The last match between the two clubs was held at the Liberty Stadium in Swansea and was decided in the dying minutes on a goal by Welsh legend Craig Bellamy, who gave Cardiff a narrow 1-0 win.

According to the former Bluebird and Jack, Andy Legg:

“It’s the fixture that guarantees goals – only three goalless draws in the past 50 league games – and noise so loud ‘it can shake your body.”

The South Wales Derby will not be up against any other Premier League match this weekend, so the Welsh clubs are taking center stage on ‘Super Sunday’. What viewers are about to witness has never taken place before in the top flight of English football. This is a derby that has been referred to as “the most-fierce rivalry in British football”. For the first time in history, the spotlight of the footballing world will be focused on South Wales.

Strap yourselves in.