James Hayter struck both goals in the opening 19 minutes as Yeovil ended a run of four successive defeats with a surprise victory at St Andrew's.
The triumph, which was only their fifth of the season, did not do much to change second-bottom Yeovil's predicament in the relegation zone as three of their main rivals also won, but Johnson was nevertheless delighted with his players' efforts.
He said: "This is our fifth win and it rates highly because all the other teams around us won.
"They (the other teams) are probably more disappointed because they were hoping to drop us out but we are hanging on.
"We are still battling and the boys showed a great spirit. That spirit will keep us in the hunt for a big part of the season. I was very proud of the boys' effort and performance."
Johnson was also keen to praise match-winner Hayter, who struck the opener in the 12th minute and then doubled his side's lead seven minutes later.
The Glovers boss said: "James Hayter has been a super striker for a long time. When he gets himself in those positions he is a very good finisher.
"He doesn't panic and he took his goals extremely well.
"We thought that if they made a mistake we had to be ready to take full advantage.
"This is how it worked out for the first goal and James got in and scored with a clever shot.
"The second goal was something we have been working on with our wide play and getting in crosses. It was lovely diving header for the second goal."
Johnson added of the victory: "It was a super win. The big thing was that we had to get to the ball first in both boxes.
"We did that in the first 20 minutes and scored twice to clinch the points.
"I thought the will to win and the mentality of the boys was fantastic.
"We always looked dangerous on the break and quietened the crowd."
The Glovers were undoubtedly helped by a calamitous mistake by Birmingham's stand-in central defender Hayden Mullins.
The veteran attempted and completely missed an intended headed back-pass to his goalkeeper Darren Randolph and Hayter ran past the Birmingham defender to slide home the opener.
Randolph was then beaten for a second time when Hayter glanced home a header from a left-wing cross by Joe Ralls.
Hayter's two-goal blast was a wake-call for Birmingham and Lee Novak hit the crossbar with a header and teenager Reece Brown hammered in a blistering shot which was well saved by Marek Stech as the hosts tried to respond.
They were unable to get back into the game though and assistant manager Terry McDermott admitted afterwards: "To say we are disappointed is an understatement.
"We actually played quite well in the first half when we created a lot of chances.
"The second half became more difficult. When you park 10 men behind the ball it is difficult to break.
"We should have dealt with the two goals and we paid the penalty."
McDermott did, however, paid rich credit to youngster Brown on his league debut.
"He was fantastic. He has a big future ahead of him," he said.
"He is a laid-back character and you cannot faze him. This is a great asset to have in the game.
"For someone so young he has an awareness which is a great gift to have as a footballer."
- Sports & Recreation