The Atlas could be called an oddball among Starfleet's ships, a nominal success but still disliked by crews. Whilst superior to the Repulse and Federation, that's not to say it was a particularly solid ship in retrospect. But, alas, hindsight is 20/20.
The Atlas class, like its rivals, owes its existence to Burnham's War, which saw substantial Starfleet losses even among the largest and most capable vessels. It was these losses that necessitated Starfleet take a close look at its options and initiate a complete redesign of its active vessels, based on plans for the Phase 1 refit of the Constitution class. The Atlas was among the largest and most well armed of these ships.
Sitting at around 370m long the ships boiled down to a very simple idea. Taking everything successful about the Constitution Class and making it bigger. The warp core? Bigger. The saucer? Bigger. The phaser count? Bigger. The Torpedo launchers? Completely the same admittedly, but the Constitution wasn't exactly lacking in that regard. The ships, compared to the overly innovative Federation Class or the Repulse Class, which sourced parts directly from other ships, struck a unique balance of innovation and more classical design standards, which some would argue held the ships back overall.
In terms of the raw numbers, the ship sported 10 FH6 phasers, clustered into 5 banks. Additionally the ship carried two dual torpedo launchers, one fore and one aft. The warp drive was actually of note on this ship, as whilst its rivals had 2 and 3 nacelles respectively, the Atlas sported 4, with two stacked vertically on either side of the secondary hull. This netted a maximum sustained speed of Warp 8 and an emergency speed of Warp 9.5, Cochrane scale. Powering this impressive combination was an SSWR-XVII-B Vertical Warp Core, mounted within the neck of the ship. The Atlas, whilst not the first to carry a vertical core, was among the first to take full advantage of it.
In terms of their actual performance it could be called unimpressive. Whilst the combat trials with the USS Atlas were exceptional their impulse engines gave them sluggish handling and their warp drive burned through more fuel than hoped. Regardless, as Repulse was Obsolete On Delivery and Federation threatened to explode if so much as looked at funny the Atlas was clearly the superior ship, and 24 more would be ordered. The ships were arranged into fleets with no more than 3 Atlas class ships present, guarded by 4 cruisers (either Constitutions, Mirandas or Shepards) and up to 6 lighter ships (typically either Saladins or Pioneers). These fleets would be placed around the various important worlds of the Federation. Atlas herself would join the two Federation class ships in the defence of Sol should anything happen.
That day would come in 2268, with the start of the third Klingon-Federation War. This would see the immediate mobilisation of 2 Atlas fleets ready to defend the Federation against Klingon invaders by any means necessary, with the fleets coming to blows in open space near Sherman's Planet. Facing an equal number of Klingon ships, the spearhead for an invasion, the fleets would engage in combat for 6 hours before, on both sides, the weapons were forcibly stopped by the Organians, revealing themselves to be higher life forms who forced the treaty of Organia. After just 168 hours the war was already over.
And with that the Atlas would never see combat again. Unlike the ever-roaming Constitutions they never got into Skirmishes and thus never had a serious reason to fire their weapons in anger. Whilst often sent as backup for tense situations or diplomatic envoys they never got the chance to show what they could truly do. The ships were never refitted to Total Modernisation Programme specifications and thus were withdrawn in the 2290's with the advent of the Excelsior. Two would go to Starfleet Academy and one of these, the USS Prince Of Wales, would be placed on display within the fleet museum at Athan Prime, where she remains today. The other, the USS Iowa, actually remains in academy use to this day, among the oldest Starfleet ships in active service. When her retirement does come it will truly be the end of an era.