In what proved an uneventful derby where both teams struggled to create clear-cut chances, a superb strike from Karlan Grant was enough to seal all three points for the Baggies.
Lee Bowyer's side headed to The Hawthorns with a clear plan to frustrate Ismael's men.
And over the course of the 90 minutes, they arguably did enough to come away with a point.
But Grant's superb strike was the one moment of genuine quality in the game and proved enough to be the winner.
“It was important to win the game," Ismael said.
"It was a difficult game, we knew exactly when you see the stats before the game - Birmingham have conceded 12 goals in five games, and we knew they’d change something.
“That was my expectation. They came for a clean sheet, to take a point, to waste time, to frustrate. It was important to stay calm and to continue putting the pressure on.
“I said to the guys at half time - we need to do it better, we need to move the ball quickly, to have quick free kicks and throw-ins, to raise the intensity in the game. We have the quality to score at any moment, so be patient.
“Even if it’s 90+, we know we can score at any time and tonight it was the case.
"I’m delighted after the goal, it was much better. It gave a second breath to the crowd, the players. We managed the game very well.
“There were a lot of positive points. Three points, a clean sheet, a local derby won. Matt Clarke came back after his injury, played brilliantly.
"Jayson Molumby came in and gave a brilliant performance.
“Now it’s time to recover because we move quickly against Swansea.
"We reached our purpose - we wanted to start the next block positively and I hope it’ll give the guys that confidence you need to take the next points.”
During the game, midfielder Alex Mowatt was replaced by Molumby after receiving a knock to the foot he first injured up at Stoke.
Meanwhile, Grady Diangana wasn't named in the Baggies squad after picking up a hamstring injury.
But Ismael expects both players to be available for selection when his side heads to Swansea on Wednesday.
"Alex is the same injury, a bruise on his toe," the boss continued.
"He took the right decision to come off, we need to manage him for the next game.
“Grady has a hamstring issue, not too bad. It’s a small issue, we didn’t want to take any risks for this game.
"My expectation is that he will come back for the next game against Swansea.”