Republic of Ireland clinched a place in the World Cup play-offs by defeating Wales 1-0 in Cardiff, but the last half-hour felt like an eternity to head coach Martin O'Neill.
Needing a win to have any chance of keeping their qualification hopes alive, Ireland took the lead when James McClean drilled a fine strike past Wayne Hennessey in the 57th minute.
Chris Coleman sent on an additional striker in Sam Vokes as Wales pushed for an equaliser, though results elsewhere meant they would have needed a win to advance as one of the best second-placed teams.
The hosts continued to dominate possession but Ireland held firm to ensure it was they who finished as runners-up to automatic qualifiers Serbia in Group D.
"I'm so proud. They were magnificent. Playing away from home, against a very strong Welsh side who were magnificent in the Euros...for us to come and win here on their territory is a great result for us," O'Neill told Sky Sports.
"The last half an hour seemed an eternity, to be perfectly honest.
"We had to withstand pressure, as you'd expect, but also at the same time we knew, at some stage, we'd have to win the game.
"It was a great goal - worthy of winning any game."
O'Neill hailed his side's achievement of retaining a chance of featuring in Russia, having been drawn in what he viewed as one of the most difficult European pools.
"When the draw was made, personally speaking, I thought outside of Spain and Italy's group, because they are two world-class sides, we had a very difficult group," he said.
"Georgia, who were down at sixth in the pot, were the strongest in their section, without a doubt.
"Teams would take points off each other, I predicted that right from the start, and anybody who finished in front of Serbia would probably win it.
"We were fourth seeds, so we've come through."