**OVERVIEW:** The P 821 *Heroj* is a submarine operated by the Montenegrin Navy. Commissioned in 1992, it represents a significant capability within the regional maritime environment.

**DETAILS:**

The *Heroj* was built as part of a broader naval program intended to enhance coastal defense and project a credible underwater presence. The design emphasizes stealth, maneuverability, and effective anti-surface warfare (ASuW) capabilities within the confines of the Adriatic Sea. The vessel was conceived to operate independently or as part of a larger task force, providing intelligence gathering, surveillance, and potential strike capabilities against enemy surface combatants. The operational doctrine assumed a contested littoral environment, emphasizing the need for advanced sensor suites capable of detecting and classifying targets in complex acoustic conditions. The selection of materials and internal layout also reflected an emphasis on crew comfort and endurance during extended deployments.

The *Heroj*'s primary roles are ASuW and intelligence, surveillance, and reconnaissance (ISR). Although not equipped for dedicated anti-submarine warfare (ASW) or anti-air warfare (AAW), its ability to remain submerged for extended periods and its torpedo armament provide a potent threat to surface vessels. The boat likely participates in exercises with allied navies to maintain operational readiness and interoperability. The *Heroj* contributes to maritime domain awareness by monitoring shipping lanes, detecting potential smuggling activities, and contributing to search and rescue operations within Montenegrin territorial waters and exclusive economic zone (EEZ).

The sensor suite aboard the *Heroj* is critical to its operational effectiveness. The installation of the Stop Light B [Nakat] radar provides surface search and navigation capabilities. The CSU 3-2 sonar and IPS CSU 3 integrated processing suite provide the submarine with an improved acoustic detection and classification range, allowing it to effectively track and target surface contacts. The Snoop Group electronic support measures (ESM) suite is used for the detection, identification, and geolocation of radar emitters, significantly enhancing the submarine's situational awareness. The PRS 3-4 sonar provides additional target tracking capabilities. The AN 407 likely serves as an underwater telephone for secure communications with other submerged units or shore facilities. A generic submarine periscope with optical and possibly electronic enhancements allows for visual target identification and reconnaissance.

**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