Who are the Bundesliga's newest arrival Union Berlin?

Union started the final day of the Bundesliga 2 season in third, which was already enough to guarantee them a place in the play-off against Stuttgart, who finished third from bottom in the top flight.

While fourth-placed Hamburg had no chance of catching them, the east Berliners were hoping to leapfrog Paderborn, who began Matchday 34 just one point above them in second place. In the end, they missed out on automatic promotion by the finest of margins.

Dynamo Dresden did their fellow East Germans a huge favour on the final day by beating Paderborn 3-1, but Union were unable to get the better of 10-man Bochum, despite late goals from Grischa Prömel and Joshua Mees setting up a grandstand finish. A 2-2 draw and a worse goal difference than Paderborn meant that Urs Fischer's side would have to do it the hard way against VfB.

Promotion marks a fitting end to a remarkable campaign for Union, whose previous biggest achievement on a national scale was reaching the DFB Cup final in 2001, when they were beaten 2-0 by Schalke. They only lost five matches in the league this season – fewer than even Bundesliga 2 champions Cologne – and “Iron Union” had the best defence in the division, conceding just 33 goals.

Former Basel manager Fischer was appointed head coach in time for the new season, and his side signalled their intent early on by claiming a draw in Cologne on Matchday 2 and by thrashing St. Pauli 4-1 a week later.

Although they were hard to beat, Union found wins difficult to come by thereafter – drawing seven of their next 10 league matches. They had goalkeeper Rafal Gikiewicz to thank for keeping their unbeaten run going, though not always in the most orthodox way. On Matchday 9, the Pole popped up with a back-post header to score a 94th-minute equaliser in the home draw with Heidenheim.

During that glut of draws in the league, however, Union’s brilliant performance in the DFB Cup against Borussia Dortmund in October suggested that they had what it takes to mix with the best. Sebastian Polter’s two goals had Union dreaming of a famous win in Dortmund, only for Marco Reus to score from the penalty spot in the very last minute of extra-time to give the Bundesliga runners-up a 3-2 win.

At the halfway point of the campaign, Union were in third position in the second tier – six points behind then-leaders Hamburg. Fischer’s team were the only unbeaten side left, having won seven and drawn 10 of their matches. On Matchday 18, though, they lost 3-0 at Erzgebirge Aue, meaning they went into the winter break with plenty of work to do.

Union started 2019 with a 2-0 home win over Cologne but after fighting back from two down at Pauli a week later, they suffered a cruel blow when Alexander Meier’s 94th-minute penalty gave the home side a 3-2 victory.

Four wins from five followed, though, and after a victory at fellow promotion hopefuls Holstein Kiel, Union were third again – only four points shy of pacesetters Cologne.

Guided by Fischer’s calm authority and featuring midfielder Felix Kroos – brother of World Cup winner Toni – Union’s style saw them try to pass out from the back. It seemed like it had put them in a good position to become only the sixth team from the former East Germany to earn a place in the Bundesliga.

Union had been close before. On Jens Keller’s watch in 2017, they went top with nine games remaining only to falter and finish fourth.

And in a punishingly competitive division, their form slipped again this year. Back-to-back defeats against promotion rivals Paderborn and Heidenheim were followed by three draws in a row, as doubts and nerves crept in with the finishing line coming into view.

Hoffenheim loanee Robert Zulj got a crucial opening goal in a 2-0 home success against Hamburg on Matchday 31, however, and – following defeat at Darmstadt – two more strikes from Polter helped Union beat Magdeburg 3-0 on Matchday 33. Victory in Bochum would have secured automatic promotion on the final day, but it was not to be.

They took their second chance, though, with Suleiman Abdullahi and Marvin Friedrich scoring vital away goals in an impressive 2-2 draw in the first leg of their play-off with Stuttgart. That set the scene for a nervous night in Berlin, but Union held on for a scoreless draw in the return match to become the 56th team to play in the Bundesliga.

They will make a colourful addition to the top flight, too, not least because fans have to cut through a forest to reach the Stadion an der Alten Försterei (Stadium at the Old Forester’s House), Union’s impressive 22,000-capacity home.

The existence of that ground in the eastern neighbourhood of Köpenick is also testament to their loyal fan base. In 2004, numerous supporters gave blood under the slogan “Bleed for Union” in order to help the club avoid bankruptcy. Four years later, 1,600 volunteers toiled for an estimated 90,000 hours to help Union save costs on the rebuild and modernisation of their stadium.

Fans also visit the ground to sing Christmas carols every year, but before they do so this December, they will get the opportunity to enjoy a first-ever taste of Bundesliga football.

Watch: Union's Grischa Prömel reacts to earning promotion

As an added bonus, they will have a couple of rare Berlin derby matches to look forward to as well. Union and Hertha met for the first time in a competitive fixture in 2010, and have only played four second-tier games against each other between then and 2013.

Tickets for the next derby meeting in east Berlin will be hard to come by, but every home match will be a celebration for Union. There's a party atmosphere evident from the moment you get off the train on a matchday and - as Stuttgart found out to their cost - it will be a tough away fixture for any visiting team next season.