SMS Szent Istvan was one of four Tegetthoff class dreadnoughts built by the Kuk (Kaiserliche und Konigliche) Kriegsmarine, the Austro-Hungarian Navy. She was built in the Ganz-Danubius shipyard in Fiume (now Rijeka), and commissioned in December 1915, well into the Great War.
The Tegetthoff class were the only dreadnought battleships ever completed by Austria-Hungary. While a large number of design studies for similar, bigger vessels, and even battlecruisers, were drawn up, a smaller-capacity industrial base for the construction of large warships and, above all, a serious limitation on infrastructure size and capacity, meant that none of the aforementioned ever came to fruition. In fact, the Tegetthoffs themselves were very limited in size due to dockyard and slipway sizes. With only a length of 152 mt, they were even shorter than HMS Dreadnought nine years before them. However, along with their Italian counterparts and adversaries, were sporting some of the most advanced features for battleships of the time. Four triple 30.5 cm turrets, superfiring both forward and aft, gave the ships a very heavy broadside for less weight than the same number of guns in twin turrets, or having all mounts at deck level, a feature present in the first generation Italian dreadnought Dante Alighieri, rectified in the successive Cavour class. The Austro-Hungarians skipped the so-called first generation dreadnoughts entirely, and laid down a class of battleships with superfiring turrets in 1914 (a still very novel feature even among the larger navies), and added a gun to each turret, a feat accomplished only by the Italians and Russians at the same time. It must be remembered that it is not as easy as it sounds adding one gun to a turret: for example, if a single is upgraded to a twin, double the parts, double the chance something is going to go wrong. And the problem rises exponentially with every single barrel added, because of the added complexity intrisinc in the design.
Szent Istvan herself had a short and somewhat uneventful career, mainly due to fuel shortages (75% of Austria-Hungary's Navy's coal came from Britain), being subjected to air bombardment of somewhat questionable value by the newly-formed Italian Air Force while at anchor in Pola. In June 1918, Rear Admiral Horthy commanded the battle fleet out of port, to attack ships of the Otranto Barrage, a naval blockade set up by the Allied powers. While en route to rendesvouz with her sisters Viribus Unitis and Prinz Eugen, Szent Istvan was slowed because of eccessive overheating of her turbine. Sister ship Tegetthoff was kept close to avoid separating the ships and making them more vulnerable. At about 3:25 in the morning on 10 June, two Italian MAS (small torpedo craft) boats attacked the battleships under cover of darkness. Tegetthoff was not hit, but Szent Istvan was hit by two 450 mm torpedoes abreast her boiler rooms. The ship quickly list to starboard and rolled over in minutes on the surface. The event was caught on camera, and is now one of the most widespread and best known piece of footage of a battleship sinking.