The pilgrimage to Prague is under way and the first of thousands of Irish fans have arrived in the Czech capital.
More fans will watch the game in the centre of the Czech capital than in the Fortuna Arena, with only around 1,200 tickets allocated to Irish supporters in a stadium which seats around 20,000 people.
More than a dozen flights are departing Dublin for Czechia this week, almost half of them are additional services. But many more fans are making their way to Prague via other European airports and are expected to descend on the Czech capital by road and rail between now and Thursday.
Some have come long distances and told elaborate stories to get here.
Among them is a man who disembarked at Prague airport with a toy parrot strapped to his shoulder.
He gave RTÉ News three different names during the course of our interview, the reason quickly becoming apparent.
"I'm from Mullingar and came from Melbourne. It cost me a fortune. First I was sweating over a ticket, then I was sweating over getting here, with all that's going on in the Middle East.
"But I got a ticket, got here and we're good to go.
"He's supposed to be at work," one of his friends interjects.
"Yeah, I've done a Stephen Ireland on it," he responds, adding "which I'm sure some people might know what that means".
Asked where his Australian employers think he is, he replied "they know I won't be there for a week or two".
Many of the fans arriving into Prague airport this morning belong to a generation that has never experienced Ireland at a World Cup.
Sean Byrne from south Dublin is one of a dozen who have arrived ticketless but are unconcerned.
"There's 12 of us coming over. No tickets, like since that goal went in in November, it's all we've talked about, so yeah, just absolutely buzzing," he said.
Sam Sherrick from Mitchelstown in Cork said he was in the Gaeltacht a decade ago, the last time Ireland were in a major football tournament.
"I suppose the last thing we seen was Euro 2016, so we were below in Irish college at the time.
"That's where I was watching so just to go abroad like, if Tuesday night works out well, if Thursday night works out well, Guadalajara will be looked up on booking.com," he said.
Cliff Kennedy, from Sandyford in Dublin, is part of a group of veteran fans arriving into Prague who have been travelling to Ireland away games for over 40 years, since before Italia '90.
Only four of the group have tickets for the Ireland end of the grounds, while some admit they have seats in the home section.
"I think we've been to many an away game that's been vital.
"But this one is a semi-final, so there's another big step after this as well but we're thrilled to be here having regard we had to beat Portugal and Hungary," he said.
"To manage both of those, it's a bonus, really, to be here."
Kevin Doyle added: "It's a bit like being back to the old times, really. You know, it's been a while since we've been in this situation, you know, so fingers crossed, we'll get through.
"It's made better, I think, by the fact that we had such a really bad few years that to be back in this position, and being in the position to maybe go all the way to the World Cup is brilliant," John Coman from Co Tipperary said.
Meanwhile, Gary Spain, Supporter Liaison Officer for the Republic of Ireland men's team, said he expects at least 6,000 Irish fans to be in Prague for one of the biggest games in a generation.
There is no formal fan zone for the travelling supporters and although the Czech capital is said to have more Irish pubs per capita than anywhere else in the world, he believes there may not be enough of them to accommodate all the Irish who arrive in the city.
"There aren't enough pubs I think in Prague's Old Town for everyone to watch the match in a pub," he said.
He said the 1,024 Irish fans who were allocated away end tickets along with an estimated 200 friends and family of players who have acquired tickets will make their voices heard in the home stadium of Slavia Prague.
"They've gone to the fans that have been to the most away games. So it's those who have been to six of the last ten under subscribed away games have been guaranteed a ticket, and those on five were in the ballot for tickets, that's the way they've been allocated. They will definitely make their voices heard wherever you go, the Irish fans will always be heard," he said.
'It won't be a beautiful game by any means'
An Irish man who will not be there on the night, but knows the Fortuna Arena and Czech football well, is Killarney native Diarmuid O'Carroll, who is currently the Assistant Manager of Czech football giants Sparta Prague.
He is also the assistant to Michael O’Neill's Northern Ireland team and will be in Italy for his own game on Thursday, but believes the Republic of Ireland squad will have a tough task against a determined Czech side
"It's a very hostile environment. They create that for the Champions League games.
"They create that for the domestic games. I would envisage something very, very similar. It'll be a loud, whistley, kind of aggressive nature to the game," said Mr O'Carroll.
He added: "They're very passionate. They're very hard working, very physical.
"There'll be an element of aggression within the stadium, and an aggression with how they play. It'll be a physical game. It won't be a beautiful football game by any means. They'll make it a little bit horrible."
In the past week the Czech FA cleared its domestic calendar to allow the players, almost half of whom play for their national league, to concentrate on the World Cup qualifier and after a period of turmoil which saw them change manager mid campaign, Czechia are now focused on progressing past the Ireland game to take on either Denmark or North Macedonia.
The current Czechia manager has described his squad as "soldiers" and the game they are entering into as "war".
Mr O'Carroll said this shows the extent of the pressure on the home side.
"Czech people are brilliant but they are passionate and they demand success, because the two clubs have done quite well in European competitions, ourselves and Slavia over the years.
"So I think they'll be adamant that they expect to go through, they'll be looking to do the business. I think there is an assumption that they will go through and I think that's maybe a little bit disrespectful to our team," he said.
Ireland go into this game as underdogs and after their unexpected success against both Portugal and Hungary it will need to be third time lucky to make it through to the final qualifying game next Tuesday.
But Mr Spain believes it is possible that Ireland can secure a place in its first World Cup in more than two decades in the US, Canada and Mexico this summer.
"I think we can. I mean, I'm really, really hoping we can. World Cups are just so special. I'm conscious of the younger fans that have never had the chance to see us in a World Cup. It would be absolutely massive. And I'm sure everyone will be dreaming of Guadalajara on the 11 June," he said.
Mr O'Carroll said while the odds are stacked against Ireland, he hopes they can prevail over his current homeland.
"I think if I was going purely analytical, I'd say it could go 2-1 either way. But listen, I'm Irish, I want them to succeed, I want to go through.
"So I think we could catch them, probably with a little bit of arrogance, a little bit of overconfidence and we'll say 2-1 to Ireland on the night," he added.
