Adam Armstrong's double gave Tonda Eckert the perfect start at permanent manager as Southampton beat Birmingham 3-1 at St Mary's.
Eckert won four out of five fixtures as caretaker, after Will Still was dismissed last month, and was given a contract until the end of next season on Friday night.
In form Finn Azaz, who grew up in Birmingham and played for Aston Villa and West Brom, got the ball rolling before Armstrong struck either side of Demarai Gray's strike.
Southampton are now three points off the play-offs, a point behind the Blues - whose terrible away form now reads as one win in nine.
The Eckert caretaker era was defined by a copious amount of goals - 15 in five games having scored 14 in the previous 17.
Paired with the last four times the two teams had met at St Mary's seeing 19 strikes, there was little chance of a goalless draw.
It only took seven minutes to confirm that likelihood as Azaz continued his fine form.
The Republic of Ireland international had not scored for Saints until Eckert's arrival, but has now notched six times in five matches.
He received the ball on the edge of the box, and after Birmingham defenders had stood off him, he placed the ball perfectly into the bottom corner with his left foot.
Leo Scienza was a nuisance for the visitors and forced James Beadle into two near-identical first-half saves when cutting in from the left. Beadle also had to tip over after Scienza tried his luck from a corner.
Tom Fellows blasted a shot against the crossbar in the 19th minute and five minutes later the hosts had deservedly doubled their lead.
Armstrong had appeared to have run out of options 25-yards from goal but he dipped his shoulder and was invited to shoot. He did, with a shot that squirmed past Beadle.
The Blues had ended the first half well, and continued their pressure into the second half and found a route back into the match in the 54th minute when Gray bagged his fifth goal of the season.
The former Everton winger cut in from the chalk of the left touchline to the box to bend one past Gavin Bazunu.
But Saint had their two-goal cushion back within four minutes. Scienza's enterprising run and shot drew a smart save out of Beadle but Armstrong was on hand to tap in his fifth goal in five matches.
Armstrong should have grabbed a hat-trick a few minutes later, after another Scienza dribble, but Beadle stuck out an arm to deny him from point-blank range. Fellows then blazed the rebound over.
The Blues were not done at the other end. Tommy Doyle's inch-perfect cross was met by Phil Neumann but his header bounced off the post, with Kyogo Furuhashi scooping over an open goal
Kyogo's next effort was heavily deflected but forced an awkward foot-save for Bazunu, before the Irishman kept out Gray's long-range effort.
But the last golden chances of the match fell to Saints. Cam Archer made Beadle make another fine one-on-one save and Jay Robinson drilled wide.
Southampton's Tonda Eckert:
"I think Southampton belongs to the Premier League.
"We need to be ambitious as a football club. We shouldn't shy away from saying that publicly.
"We know we are still quite far away but that doesn't mean that we can't talk about the ambition. We just have to back that up every single day.
"I knew I wanted to do everything for this club since the first day, whatever the role. The responsibility has grown now a bit. I feel well prepared and will put the club where it belongs.
"I decided to come for the project to develop players and my intentions haven't changed [now I'm manager].
"I'm very pleased. We played against a good side today. I told the boys not to underestimate the win today."
Birmingham's Chris Davies:
"We had more of the ball, more territory, more touches and more shots but we haven't managed to defend well in decisive moments and gave ourselves too much to do.
"It was always going to be a challenge but the first 20 minute we weren't strong enough physically or quick enough onto the ball and we paid the price for it as we were 2-0 down against a team with loads of good players away from home.
"That first 20 minutes is now what we have been talking about or what we wanted to deliver.
"They had a couple of moments that we have to defend better. We had a lot of Blues shirts back on all the goals, it wasn't like we were opened up.
"After that there was a game of a lot of positives. We really took the game to them, there were a lot of things to like about our performance.
"The absolutely decisive goal is the 3-1. It takes the stuffing out of us when we had a really great chance to win.
"We went to the very end but it wasn't enough."
