A youthful Pompey side eased past Southend at Roots Hall to reach the last eight of the Checkatrade Trophy for the first time.
They went ahead through Louis Dennis almost immediately from kick-off and never looked like relinquishing that lead.
Gareth Evans then wrapped things up on the stroke of half-time before a turgid second period that did little to excite the small Essex crowd.
Kenny Jackett made 10 changes from the side that secured a dramatic FA Cup victory at Norwich at the weekend.
Evans – who wore the captain’s armband – was the only man to keep his place, although substitute goalscorer Andre Green also featured.
Dan Smith was handed a debut at right-back, with fellow teenagers Matt Casey and Bradley Lethbridge also given an opportunity to impress.
Christian Burgess, Brandon Haunstrup and David Wheeler added first team experience to a young side, with Dennis, Adam May and Alex Bass making up the starting 11.
The hosts – by contrast – were fielding a much more experienced side and yet found themselves behind with just 93 seconds on the clock.
Wheeler played the ball to Smith on the right and his smart delivery into the box was nodded into the net by DENNIS to open his Blues account.
Pompey looked the more dominant outfit throughout the first half and a free-kick from Evans was unconvincingly punched behind by Ted Smith.
May screwed a shot wide of the post after being teed-up by Lethbridge, who then fired a fierce effort narrowly over the bar.
It looked like the lead would be doubled on 28 minutes when Wheeler raced on to Green’s threaded pass, but the winger slotted inches past the post.
Southend had done little to threaten the visitors’ goal, although a short free-kick routine almost saw them level.
The ball was played to former Fratton triallist Theo Robinson and his low delivery somehow evaded both Harry Bunn and Taylor Moore as they slid in at the far post.
Pompey immediately went up the other end to create an opening of their own, as Burgess met an Evans corner and saw his header cleared from the line by a well-placed Robinson.
But they did score again in stoppage-time when Dennis showed neat footwork to tee-up EVANS, who lashed the ball past a helpless Smith.
Southend Uited 0
Jackett made a change at the start of the second half, with academy midfielder Freddie Read replacing Green.
And Evans almost got the half off to the perfect start, curling a free-kick past Smith’s grasp and just wide of the upright.
Leon Maloney then became the second Blues player to make his debut, with the youth team forward coming on for Lethbridge.
It was still the visitors looking more likely to add to the scoring and May fired over when Casey sent Evans’ free-kick back into the centre.
The traffic was not totally heading in one direction, however, and Burgess had to block a Stephen McLaughlin shot following a spell of Shrimpers pressure.
But, in truth, neither side was doing much to raise the tempo as the minutes ticked down with very little in the way of noteworthy incidents.
Southend did win a series of corners towards the end of the contest, but it was proving to be a comfortable evening for Bass between sticks
A long-range volley from Read was not too far off target, but Pompey had already done comfortably enough to ensure their name would be in Thursday evening’s quarter-final draw.
Southend (4-2-3-1): Smith; Bwomono, White, Moore (Hutchinson 60), Hendrie; Hyam, Yearwood (c); Kightly (Dieng 46), Cox (McLaughlin 46), Bunn; Robinson
Subs not used: Bishop, Turner, Mantom, Klass
Pompey (4-2-3-1): Bass; Smith, Casey, Burgess, Haunstrup; Evans (c), May; Wheeler, Dennis, Green (Read 46); Lethbridge (Maloney 54)
Goals: Dennis 2, Evans 45+1
Subs not used: Durin, Mnoga, Clarke, Hancott, Lowe
Referee: Craig Hicks
Attendance: 1,649 (189 Pompey fans)