Birmingham's first European home game in nearly 50 years ended in success as they beat Nacional to make it through to the Europa League group stage.
Having drawn 0-0 in Portugal a week ago, City seized control of the tie via Nathan Redmond's superb drive and a David Murphy header from a corner.
Redmond could have added to the score in the second half but curled an effort against the inside of the post.
Chris Wood did add a third from close range late on to complete a fine win.
In the away leg Chris Hughton's side had hit the woodwork three times but they thrived in a near-capacity St Andrew's, scoring twice in nine first-half minutes to give them a firm grip of the contest.
It was fitting that the lively Redmond, a life-long Blues fan who impressed throughout the match, should be the one to give them the lead with a superb 25-yard strike that found the bottom corner of the net.
Soon after, the lead was doubled as Murphy was credited with a near-post header from Jean Beausejour's corner.
The Blues had plenty of opportunities to add to their lead, with Chris Burke seeing an effort cleared off the line, Nacional keeper Elisson saving well to deny Adam Rooney and Redmond curling a fine effort against the post.
However, Wood rounded off a superb night for City with a close-range finish following a swift counter attack and Blues can now look forward to Friday's draw for the group stage.
Birmingham manager Chris Hughton: "I'm extremely proud. We knew it was going to be a very tough game.
"It was similar to the first leg where Nacional started very well. We took a little while to get into the game but once we did, I thought we were very good value for the win.
"I think if you look at the atmosphere tonight and the performance, you had a team that very much wanted to go through and a full house that very much came to cheer the team on and, if you asked any of them if they wanted to go through, it would be an emphatic 'yes'."
Nacional manager Ivo Vieira: "The fact they are in the second division doesn't mean they are a weak team.
"They beat Arsenal to win the cup. We knew they were strong.
"It was difficult, we tried to impose ourselves but we weren't able to and they got the better of us."