And at the same time they dealt a massive blow to Hartlepool's play-off hopes.
They had looked down and out before half time when Pool were in total control.
But the arrival of Richard Logan and Calum Willock did the trick for Posh.
The home team looked out of sorts in the opening exchanges as Peterborough pushed forward and created a string of half chances.
But Hartlepool survived without too many problems and on 22 minutes the match suddenly turned in their favour as they took the lead with the first effort on target.
Matty Robson's free-kick from the left was curled to the far side of the area and Mickey Nelson headed it back into the middle for defensive partner Chris Westwood.
He headed it on again and in-form Aussie Joel Porter had time to turn well and score from 10 yards.
On 36 minutes, Porter combined with fellow striker Adam Boyd, whose tricks were causing all sorts of problems for the visitors, to set up the second.
Boyd's pass sent Tony Sweeney surging into the box and just when it seemed he'd been beaten to the ball by the advancing Mark Tyler, he stuck out a foot and slid it under the keeper into the net.
But those two inspired changes at half time turned the game on its head.
Logan narrowed the gap on 49 minutes with a snap-shot from 25 yards.
And on 56 minutes Willock got on the end of a bouncing ball deep in the penalty area after a corner and headed in from close range.
That really put the wind up Hartlepool and they were never the same team again.
In fact, they were lucky not to go behind midway through the half when Willock blasted in from an angle on the left but the goal was ruled out for a foul by a team-mate in the build-up.