Wes Thomas came up with two crucial first-half goals to pave the way to Birmingham's comfortable 2-0 Capital Cup second-round home win over a battling Gillingham.
Birmingham's success enabled them to maintain their unbeaten start to the season but it was Gillingham's first taste of defeat.
Gillingham, currently top of League One, gave a good account of themselves and demonstrated why they have made such a good start to the season but they had no answer to the goalscoring exploits of Thomas who took his career tally to 51 in this tie.
The feature of the early play was the confident attitude of the Gillingham side to take the game to Birmingham with the home defence finding themselves under pressure.
This lively play very nearly led to an early goal when Koby Arthur made a poor cross-field pass which let in Ben Williamson but the striker's snap shot was hastily deflected by a relieved Birmingham defence.
Both teams made several changes from the weekend which resulted in some promising young talent being given their chance to shine.
The exception was the much travelled Birmingham goalkeeper, Adam Legzdins, who made his debut and found himself being forced to make several saves to keep out the eager Gillingham side which pleasingly attacked in depth.
It was not until the half hour that Birmingham began to assert their authority as demonstrated by a long-range effort from Andrew Shinnie which dipped agonisingly just over the bar.
The Gills were certainly indebted to their two central defenders, Max Ehmer and in particular Adedeji Oshilaja.
But the stalemate was broken in the 35th minute when Birmingham confirmed their growing dominance.
Jacques Maghoma's corner from the right was pushed back towards Gillingham's goal by Paul Robinson and Thomas was on hand to nudge the ball home past Stuart Nelson from close range to give Birmingham the upper hand.
The goal took a lot of fire out of Gillingham as Birmingham took control of the mid-field exchanges just before half time.
Surprisingly Birmingham were again slow starters despite a couple of off-target efforts from Thomas and Shinnie.
As a result Gillingham were allowed to step up the pace. A careless back header by Mitch Hancox let in Williamson and his low cross-shot beat Legzdins but went just wide of the far post.
Substitute Cody McDonald raised Gills' hopes when he broke clear on a counter attack and fired in a powerful drive which Legzdins pushed around the post.
Gillingham's bid to snatch an equaliser led to their downfall as unmarked Thomas notched his second goal in the 72nd minute with a nonchalant shot past Nelson.
Late in the game Birmingham drafted in their latest signing, Nicolai Brock-Madsen and the Dane made a promising impression.