OVERVIEW: The P 821 Heroj is a submarine of Yugoslav origin, commissioned in 1969. The vessel represents a significant component of Yugoslavia's submarine force during the Cold War era.

DETAILS:
The *Heroj* class submarines were developed by Yugoslavia's Brodarski Institute (Brodarski Institut) in Zagreb, reflecting a national ambition to create an indigenous submarine design and production capability. The design philosophy emphasized a balance between cost-effectiveness, operational flexibility in the Adriatic Sea environment, and survivability. They were designed as a successor to the earlier *Sutjeska* class, incorporating improvements in sensor technology and underwater endurance. The *Heroj* class represented a considerable step forward in Yugoslav naval engineering, showcasing the country's capabilities in shipbuilding and defence technology. Their compact size was tailored to the relatively shallow and confined waters of the Adriatic, where maneuverability and concealment were paramount.

The primary role of the *Heroj* was anti-surface warfare (ASuW), with a secondary emphasis on anti-submarine warfare (ASW) within the Adriatic theatre. Their mission profile encompassed patrolling strategic chokepoints, disrupting enemy surface ship movements, and providing early warning of potential amphibious assaults. Given the regional geopolitical context, these submarines were also postured to conduct covert reconnaissance and insertion of special operations forces if required. The 533mm torpedo tubes were the primary means of engaging enemy vessels, likely employing both conventional and potentially wire-guided torpedoes depending on availability.

The suite of sensors fitted aboard the *Heroj* enabled a reasonable level of situational awareness for its time. The installation of the Stop Light B [Nakat] radar would have provided surface search capability, allowing the submarine to detect and track surface vessels at a distance. The CSU 3-2 sonar system would have been utilized for underwater target detection and tracking, providing both active and passive sonar modes. Supplementing this was the IPS CSU 3 integrated processing system to manage sonar data. The PRS 3-4 sonar, functioning probably as a ranging or intercept array, improved target location accuracy. The presence of AN 407 suggests an IFF (Identification Friend or Foe) interrogator for determining the identity of radar contacts. The Snoop Group radar intercept receiver (RWR) enhanced the submarine's ability to avoid detection by identifying enemy radar emissions. The Generic Submarine Periscope, Optical, provided visual confirmation of targets and aided in navigation when surfaced or at periscope depth.

SPECIFICATION: Length: 50.4 m || Beam: 7.2 m || Draft: 5.0 m || Disp: 614 t

SENSORS: Stop Light B [Nakat] || CSU 3-2 || Snoop Group || PRS 3-4 || AN 407 || IPS CSU 3 || Generic Submarine Periscope, Optical

ARMAMENT: 533mm TT