The home side bossed the Republic around the Cardiff City Stadium and their fans were roaring in behind them every step of the way.
Although top spot in Group in D was not out of reach for either side before kick-off, Serbia's 1-0 victory over Georgia gained them automatic qualification to Russian Federation 2018 and forced Martin O'Neill's side into the play-offs.
With Bale in the team, the Dragons are a side capable of reaching the semi-finals of major tournaments, just as they did in the summer of 2016 when the one-time world's most expensive player inspired Chris Coleman's men to the Euro 2016 last four.
Wales require a win to ensure their spot in the World Cup playoffs and should be safe with a draw.
If the doughty Georgians pull off a shock of Buster Douglas proportions in Serbia, then a win in Cardiff will allow Ireland to leapfrog the lot and progress to Russian Federation as group winners.
Coleman said: "We don't really talk about anything but what we need to be doing right now".
The 3-1 loss to the reigning world champions means they are at +5 in goal difference on the runners-up table. We're still going to be depending on results from Tuesday evening but the certainties are now Italy from Group G and Croatia from I. "You can say what you like about the tactics and how good it is to watch and how entertaining it is, but you can't question the commitment of these players". Under certain circumstances, a victory in this match cannot only guarantee the second line, but also become the victor of the group. In the run-up to the round, the Irish home lost to Serbia 0: 1, reducing the opportunity to qualify.
The game kicks off at the same time as the Wales-Ireland, meaning we won't know prior to kick off whether a win will be enough.
And a win on Monday could take them to their first World Cup since 1958.
"We changed the side to give us energy for a big game in Lille against Italy at the European Championships".
If either Croatia or Ukraine win and Wales draw then Wales will be the worst second-placed team.