The Regioni class started out as a design originally inteded for export, most likely candidate being the USSR, but they chose to go their own way with the Kronshtadt class battlecruiser. While the Italian design in most ways could be considered a battlecruiser, they were called cruisers so as not to alarm the British and French to their true nature as not only cruiser-killers, but also potentially oceanic raiders, not only fast enough to overtake most cruisers (at least in rougher seas,) but also fast enough to out-run the battlecruisers and fast battleships of noth the Royal Navy and the Marine Nationale. In many ways they could be compared to the German duo Scharnhorst and Gneisenau (more specifically the 11" guns originally designed for export designs mirroring the Deutschland class.)
The ships displaced 25000t standard, and 27000t full. The oa length is 237,5m, a width of 28,1m and a draft of 8m at normal load.
The armored belt was 7" thick, and covered almost all spaces between turrets 1 and 3. Most of the remaining waterline was protected by a 2" thick strip of armor (mostly for protection against splinter damage from near missed from either shells or bombs.) The deck was protected by 3" of armor. The turrets had barbettes of 7", faces of 7", sides of 5" with the rear and top of 3" of armor. The 120mm mounts had 5" of armor on the front, and 2" on the sides and rear. The conning tower was protected by 7" of all-round armor.
The ship had 8 boilers and 4 geared turbines producing a total of 206k shp driving 4 shafts for a top speed of 35kts. At 12kts the ship had a range of 10k nm.
Main armament consists of 9x11"/50 guns in three triple turrets, two fore and one aft.
The secondary armament consists of 12x4,7"/50 DP guns in stabilized single mountings. The mountings themselves were of similar design to the 90mm gun used on the Littorio and rebuild Andrea Doria classes, and boasted great ballistic performance and had the added bonus of being large enough to fire effective star-shell ammunition (Though the casings needed reduced propellant capacity so as to not damage the rather fragile star-shells.)
The medium AA battery consists of 10x65mm guns in shielded single mounts. The 65mm gun was developed as a replacement for the 37mm guns, whose twin and quad mountings were considered less than ideal by the Regia Marina due to excessive vibrations caused by the fixed barrels and gas-operation. In addition they had low ammo-capacity in their magazines and were considered to have insufficient range and stopping power. The light AA concists of 36x20mm guns in 18 twin mounts. Generally seen quite favourably by both sides of WW2, the gun was often likened to the German 20mm gun and the Oerlikon 20mm gun for its effectiveness.
A pair of triple torpedo-launchers were to be included, but due to shifting priorities and the changing nature of naval warfare meant that they were no longer considered important, and thus not included (with the added bonus of lessened weight, and reduced fire/detonation chances.)
The Campania had an internal hangar with space for 2 Ro.43 floatplanes with optional space for two more to be stored outside on raised pedestals. Due to trauma from British aviation, the Campania (like the Littorios) would carry between 1 or 2 Re.2001 fighters in place for the same number of spotter planes for self-defense against air-attack.
Due to the late completion the ship was outfitted with the standard EC-3 ter "Gufo" radar and a pair of experimental EC-5 fire-control radars mounted to the fore and aftermost directors.
She entered service in the summer of 1943, and had completed her trials and breaking-in before the Regia Marina sailed for Malta, and later Alexandria for internment, where she along with the two remaining Littorios were considered for use by the Allies in the Pacific as escorts for the fast carrier groups, but this was ultimately rejected. The ship remained in Alexandria for the duration of the war, where she would await an uncertain fate, yet to be determined.