The derby experienced a resurgence at the start of the 21st century, with both teams reaching the Championship before eventually meeting in the top tier of English football in the Premier League for the first time in 2013 which Cardiff went on to win.

[2] With growing interest in association football in the traditionally rugby union stronghold of Swansea, the decision was taken to form a club.

The two clubs faced each other for the first time on 7 September 1912, in Swansea's first competitive fixture, with the match ending in a 1–1 draw; Billy Ball gave the Swans the lead before Cardiff captain John Burton equalised.

[3][4] Swansea went on to claim the first victory between the two sides five months later when they defeated Cardiff 4–2 in the semi-final of the Welsh Cup despite trailing 2–0 at half time.

[5] Such was the friendliness between the two sides in the early meetings that when Burton scored a bicycle kick in the match, several of his opponents stopped to shake hands with him in appreciation of the goal.

[7] Although the clubs met in the fourth qualifying round of the FA Cup the following season, it would be the last competitive fixture between the two sides for six years as the Southern Football League was suspended during the First World War.

Two friendlies were played in April 1919 as the clubs began to prepare for a return of competitive football at the end of hostilities with both sides winning a match each.

A friendly was also held in October 1919 as a benefit match for Cardiff's trainer George Latham who captained his side for the fixture in a 1–1 draw.

[12] As a result, the derby was only played a further four times before the outbreak of the Second World War; the clubs were drawn against each other twice in the Welsh Cup, with both ties requiring a replay to decide a winner.

The last competitive pre-war derby took place on 23 February 1939 as Cardiff defeated Swansea 4–1 in the fifth round of the Welsh Cup following braces from Harry Egan and Tex Rickards.

[20] This included an 8–0 victory for Cardiff in a match that was dubbed the "Bluebirds Blitzkrieg" following hat tricks from Beriah Moore and Billy James.

[23] Despite this, Cardiff manager Billy McCandless chose to leave the club to join Swansea after receiving a lucrative offer from the rival side.

[25] The figure is the biggest crowd ever recorded for a South Wales derby in which Cardiff claimed a 1–0 victory through a goal by Tommy Best.

The decision, along with the perceived favouritism from UK governments believed to have been shown to the city since has been credited as the starting point of the deterioration of relations between the two sides.

Cardiff went on to win the match 3–2 despite being reduced to ten men within the opening 30 minutes when forward Gerry Hitchens suffered a broken leg.

The next meeting between the sides, in March 1959, resulted in Swansea achieving the same feat by winning at their rivals home ground for the first time in league competition.

Cardiff's Colin Hudson was sent off for a foul with ten minutes remaining before his teammate Steve Mokone and Swansea's Harry Griffiths were also dismissed after wrestling each other to the ground and throwing mud in retaliation.

[27][32] Swansea historian Gwyn Rees has stated that fans' animosity began to increase in the late 1960s, citing the 1969 Welsh Cup final as a turning point.

[39] Significant damage was caused to local shops as well as public transport; John Williams, who played for both sides during his career, described how fans "would fight in the streets, the train station and all the way down the motorway.

[48] Despite this, the rivalry still attracted attention; during their celebrations after winning the Football League Trophy in 2006, Swansea players Lee Trundle and Alan Tate brandished a Welsh flag with an anti-Cardiff message and Trundle also wore a T-shirt with an image of a Swansea City player urinating on a Cardiff City shirt.

[49] The FAW stated that the images paraded at the match, which took place at Cardiff's Millennium Stadium, were "of an extremely offensive and insulting nature".

[50][51] A heavy police presence was also required when Swansea fans travelled to Cardiff when they played at the Millennium Stadium in the Football League Trophy final in 2006.

[53] A league fixture, on 5 April 2009 at Ninian Park, was marred by referee Mike Dean being hit in the head by a coin thrown from the crowd, as well as Cardiff fans clashing with police after the match.

[60] Cardiff won the first ever top tier meeting between the sides 1–0 on 3 November 2013, thanks to a headed goal from former Swansea defender Steven Caulker.

He began his career with Cardiff in 1956 but joined Swansea in 1959 and scored his first derby goal the following year in a Welsh Cup match.

[44] Transfers between the two sides are relatively rare, the last player to move directly across the South Wales derby divide was Warren Feeney who was loaned to Swansea from Cardiff for a brief spell in 2007.

Dave Penney captained Swansea during the 1997 Football League Third Division play-off final and made over 100 appearances for the club before joining Cardiff.

When he attempted to celebrate his first goal for the club in front of home fans, he was met with abuse and even received a razor blade in the post.

"[75] The rivalry is prevalent among the club's staff as well as fans; David Giles has described how he was warned away from speaking to former friends at Swansea when arriving at Vetch Field as a Cardiff player.

The clubs' relative league positions meant that Newport have rarely played Cardiff or Swansea since 1989, though they have faced each other in cup competitions.