In a thrilling encounter, Notts County picked up their first league away win of the season with a tremendous display at London Road.
Without an away win in the league so far this season, the Magpies were desperate to add three points to their total. However, second placed Posh had not dropped a point on home soil, winning four out of four.
Craig Short made three changes from the side that lost 2-1 to Bristol Rovers on Saturday, the most notable coming in goal, with Rob Burch replacing Stuart Nelson. Kevin Smith started ahead of Jake Jervis as the leading striker and Mike Edwards kept his spot alongside Krystian Pearce at the heart of defence, after filling in for Graeme Lee when he was sent off at the weekend.
Both teams started at pace, though it was the hosts that threatened first. Winger Lee Tomlin rode a heavy challenge and unleashed a stunning drive that flew inches wide of the post.
Notts were working hard in closing down a confident passing outfit and successfully frustrating them. Despite this lingering danger, County were not afraid of pushing men forward but a number of promising offences lacked the decisive final ball.
Such defensive resoluteness resulted in limited goalmouth opportunities in the opening 30 minutes. Home captain Grant McCann attempted to liven things up with a pop from range but he failed to test Burch, who gathered inside his six-yard box.
Ben Davies was able to spark the game into life, though, kick-starting a thrilling close to the half. Gathering a poor clearance from an Alan Judge centre, Davies took a composed touch before slamming the ball between Joe Lewis' legs for the opener.
Davies' next strike was even better, after Neal Bishop had won possession in midfield and proceeded to slide the ball into the path of the winger. With his first touch, Davies whipped the ball forcefully into the bottom-right corner from outside the box, giving the stretching Lewis absolutely no chance.
Gabriel Zakuani halved the deficit with the third goal inside five minutes from a McCann free kick. The centre-back rose strongly at the back-post and Burch could only parry his header into the roof of the net.
It looked set to be a nervy close to the first 45 for Notts and the visiting supporters' hearts were in their mouths moments later. Kelvin Langmead was left unmarked at the front post and he almost converted Tommy Rowe's cross with his head.
Controversy followed at the other end of the pitch as another teasing delivery by Judge saw Davies direct onto the foot of Smith, who slid the ball home from close-range. Although it appeared he was being closely monitored by Chris Whelpdale, the linesman's flag ruled out the finish, much to the protests of Smith, who earned a booking for his dissatisfaction.
Still, County were able to grab a third through the hard-working Craig Westcarr on 43 minutes. The forward held off Zakuani as he chased a long clearance and hooked the ball into the bottom-right corner with his left boot - arguably the finest of his five goals so far this term.
In the 52nd minute, Posh nearly reduced the lead again when Rowe collected the ball 30 yards out and volleyed at goal. Dipping over the retreating Burch, the full-back's thumping effort was only kept out by the roof of the bar.
Peterborough's luck did change shortly after, in the form of a mishit free kick by McCann. The midfielder slipped when attempting to strike the ball, leading to the ball looping towards Craig Mackail-Smith, who nodded across goal for his eighth of the campaign.
McCann's involvement didn't last much longer, because on 66 minutes he was shown a straight red card for a dangerous lunge on Judge. Tempers flared and a melee of pushing and shoving ensued, which resulted in Ricky Ravenhill and Aaron Mclean being cautioned.
And it looked as though Notts were going to be down to 10-men for the third fixture running when Ravenhill appeared to push Mclean on the edge of the area. Following much deliberation with his assistant, the referee decided that a free kick alone would suffice - immediately aggravating the home support.
A tense finish was guaranteed and it appeared that more goals were possible. Mclean's rifled set-piece was smartly blocked low down by Burch and Judge's deflected punt was headed behind by Zakuani.
The Magpies vigilantly played out six minutes of added time with some bold claims by Burch and commanding clearances by the backline. During the closing stages, dissent led to a second red card of the game following a second yellow card for Ravenhill.
The final whistle brought cheers of relief from the away end but sights were sharply shifted to the tunnel area, where a mass brawl had broken out, involving management and players. Still, the main talking point will undoubtedly be Notts' first away win and a fantastic performance against one of the division's top teams.
Attendance: 6,136 (675 Notts County supporters)
Magpie Player Man of the Match: Ben Davies