Alex McLEISH has armed himself with as much fire-power as possible to escape the Championship - and it is finally paying off.
A relieved St Andrew's saw it all come together to leave new Hornets' boss Brendan Rodgers still searching for his first victory.
Strikers Kevin Phillips, Marcus Bent and sub Cameron Jerome all found the net as the difference between the haves and have-nots was spelled out emphatically.
Watford could have snatched the draw had they been able to call upon any of the host's forwards.
But as it was, they became the Blues' latest fall-guys as McLeish's men maintained the pressure on leaders Wolves.
The home boss claimed afterwards that he had only 16 players to name after a flu bug swept through his dressing room.
But the star of the show was undoubtedly Phillips.
His positional sense, link-up play and prowess in front of goal was a throw-back to the days when he was terrorising Premier League defences.
McLeish said: "The first two goals were great strikes, of the highest order. Bent and Phillips are looking like certain starters at the moment because of their goals and overall play - and Cameron is giving me a pleasant headache, too."
Brum went into the game with the best defensive record in the division - but that boast was blown apart after six minutes.
Home defenders simply stood and watched as Tamas Priskin headed John Eustace's left-wing centre goalwards.
Maik Taylor made a great stop, but even then his colleagues failed to react as the Hungarian tapped home the rebound.
But within two minutes, Phillips had levelled.
Nicky Hunt's deep cross should have been gobbled up, but the former England international read the situation, looping a header into the corner of the net.
Ten minutes later, Bent, whose life seems to be on a decidedly upwards curve now he is starting regularly and model Gemma Atkinson has agreed to marry him, smacked a thumping drive into the bottom corner of the net. The game settled down after that, and the Hornets saw Leigh Bromby's 30-yard free-kick rattle the bar.
Then Taylor pulled off a remarkable reflex stop to prevent Rahdi Jaidi from putting the ball into his own net.
Just seconds after having a 'goal' wiped out for pushing, Jerome found himself on the left, and curled home an exquisite shot that should have sealed the points.
However, young Ross Jenkins lashed the ball home from six yards after a corner to set up a fraught finale.
Rodgers, whose team pushed Tottenham in the Carling Cup in midweek, said: "That was a very valid show and demonstration of what a great side we could be.
"I have told the players we are only a fraction away from being a very good team. I have only been here 10 days, but I have already seen progress.
"That's all you can ask for. We need to be killers at the back - in the nicest possible sense."
Birmingham: Maik Taylor 7 - Hunt 6, Martin Taylor 6, Jaidi 7, Queudrue 6 (Parnaby, 78mins, 5) - Larsson 6 (Augustien, 87mins), Carsley 7, Quashie 5, Owusu-Abeyie 5 - Bent 6 (Jerome, 72mins, 7), *PHILLIPS 9.
Watford: *LOACH 8 - Doyley 6, Bromby 6, Mariappa 6, Sadler 6 (Hoskins, 78mins, 5) - Bridcutt 7 (O'Toole, 68mins, 5) - Jenkins 5, Eustace 5 (McAnuff, 46mins, 6), Harley 7 - Smith 6, Priskin 6.
Referee: S Mathieson 7.