Pompey produced a stunning comeback to secure a memorable National League triumph at Keynsham.
The hosts had boosted their changes of beating the drop by securing a two-goal advantage at the interval.
But Shannon Albuery reduced the deficit before a brace from Cherelle Khassal completed the turnaround.
Jay Sadler made three changes from the side that eased to victory over London Bees a fortnight earlier.
Rebekah Tonks, Anisha Hill and Emma Jones all returned to the starting line-up, with Sammy Quayle, Dani Lane and Anaisa Harney making way.
The Blues got off to a terrible start and the contest was just a few seconds old when Laura Williams scored for struggling Keynsham.
The picked things up after that setback, however, and a shot from Albuery was saved, while a series of corners also caused problems.
Pressure continued to be applied and after driving inside with plenty of purpose, Emma Jones saw her attempt rattle the crossbar.
Skipper Danielle Rowe then appeared certain to equalise, only to be denied by a tremendous clearance off the line.
But, just seconds later, Pompey found themselves further behind, with Kerry Bartlett converting a penalty.
Half Time: Keynsham 2 Pompey 0
The visitors had it all to do once the action restarted and they needed to remain patient before finding a lifeline just before the hour mark.
There was no surprise about who got them back into the game, with top scorer ALBUERY poking the ball home from a few yards out.
Sadler went to his bench in an attempt to inject some more energy into his side, as they sought a leveller.
Tamsin de Bunsen was among the players who were introduced and she soon fired a shot narrowly past the post.
Fellow newcomer Quayle also had a chance to find the net, but could not quite turn Emma Jones’ low delivery on target.
And it was Jones who provided the assist for the equaliser on 72 minutes, cutting in from the left and feeding KHASSAL for a neat finish.
But Pompey were not going to be satisfied with a single point and they kept pushing forward to find a winner.
It soon arrived and there were no complaints about the scrappiness of the goal, with KHASSAL firing home following an almighty scramble.
The Blues then saw out the closing stages with relative ease to ensure a valuable win ahead of an exciting week that sees the Hampshire Cup final precede a Fratton Park clash with MK Dons.
Pompey: Haughton; Tonks (Quayle 58), Younger, Gane, Rowe (c); F.Jones (Lane 46), Hill (de Bunsen 58), Rolf; E.Jones (Coalter 90+1), Albuery (Walters 90+1), Khassal