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Türkiye Strengthens Naval Power as TCG Hızırreis Becomes Second Reis‑Class Submarine in Service.
Türkiye formally accepted the Reis-class submarine TCG Hızırreis at Gölcük Naval Shipyard, marking the second Type 214TN boat to join the fleet. The delivery strengthens Ankara’s undersea posture at a time when the Black Sea and Eastern Mediterranean are increasingly shaped by quiet diesel electric platforms.
On November 27, 2025, at Gölcük Naval Shipyard, Türkiye formally received the Reis-class submarine TCG Hızırreis (S-331), the second of six Type 214TN boats built under the New Type Submarine Project (YTDP), in a handover attended by representatives of the Defence Industry Agency (SSB), the Turkish Navy, Gölcük Naval Shipyard and TKMS. The transfer followed months of harbour and sea acceptance tests and was announced both by Turkish media and by TKMS, which underlined that the delivery confirms the programme is now progressing within the expected cost and schedule envelope. Coming just over a year after the commissioning of the lead boat TCG Piri Reis in August 2024, the entry into service of Hızırreis marks a new stage in Türkiye’s long-running effort to renew its diesel-electric fleet and introduce air-independent propulsion (AIP) capabilities on a large scale. For Ankara and its partners, this handover is more than a technical milestone: it feeds directly into the balance of power in the Black Sea and Eastern Mediterranean, where underwater superiority is becoming a central element of regional deterrence.
Türkiye’s handover of the AIP-equipped TCG Hızırreis adds a quieter and longer-endurance submarine to its fleet, tightening the country’s undersea presence in the Black Sea and Eastern Mediterranean (Picture Source: Turkish MoD / TKMS)
TCG Hızırreis is a Reis-class (Type 214TN) diesel-electric submarine with AIP based on polymer electrolyte membrane fuel cells and high-capacity batteries, enabling prolonged submerged operations without snorkeling. Built at Gölcük with an advertised local content of around 80 percent, the design combines German Type 214 technology with an extensive suite of Turkish-developed systems provided by companies such as STM, Aselsan, Havelsan, AYESAŞ, TÜBİTAK BİLGEM and MilSOFT. The submarine is about 67–68 metres long with a beam of 6.3 metres, displaces roughly 2,000 tonnes submerged and can accommodate up to 40 personnel, reflecting both the core crew and additional specialists depending on mission profile. A single-hull, one-compartment architecture optimised for low acoustic signature is combined with a modern combat system and sonar suite derived from TKMS’ ISUS family and integrated with national subsystems, making Hızırreis a key node in Türkiye’s undersea surveillance and strike network.
The boat’s armament is centred on eight 533 mm torpedo tubes housed in the forward Section 50 weapons module. In addition to legacy heavyweight torpedoes, the class is being associated with Roketsan’s Akya heavy torpedo and submarine-launched variants of the Atmaca anti-ship missile, often referred to in Turkish sources as “Sub-Atmaca” or AKATA. In the longer term, integration of the land-attack Gezgin cruise missile remains a stated ambition for the Reis class, which would add a deep-strike dimension against coastal and inland targets. Alongside this missile and torpedo load-out, the design retains the ability to lay naval mines, giving Hızırreis a wide spectrum of anti-ship, anti-submarine, area-denial and potential land-attack options from a concealed underwater position.
The delivery of Hızırreis submarine results from a sustained industrial and operational strategy under the YTDP framework, established between Turkey's SSB and Germany's TKMS in the early 2010s, designating Gölcük Naval Shipyard as the primary construction site and STM as the principal local partner since December 2009. This agreement facilitates the construction of six Reis-class submarines in Turkey with progressively increasing domestic content; the lead vessel, TCG Piri Reis, commenced construction in 2015, launched in 2019, began sea trials in December 2022, and achieved commissioning in August 2024 after approximately 62 months, comprising 42 months for construction and fitting out, nine months of harbor acceptance, and eleven months of sea trials. Hızırreis adhered to an accelerated schedule, launching on 25 May 2023, completing outfitting at Gölcük, and initiating sea trials in 2024, including its first trial on 17 September and initial dive the following day, before progressing through an intensive acceptance and capability verification phase under TKMS supervision, culminating in handover to the Turkish Navy on 27 November 2025.
By late 2025, Hızırreis had spent roughly a year in combined harbour and sea acceptance tests, after which she was formally transferred from Gölcük Naval Shipyard to SSB and simultaneously to the Turkish Navy in a compact ceremony at Gölcük. TKMS highlighted that it remains responsible for construction support, material delivery and the test campaign, and that the submarine now enters an 18-month warranty period as she settles into front-line service. The company’s submarine division leadership emphasised that the second-boat delivery demonstrates the learning curve from Piri Reis and confirms that the binational industrial partnership is on the right track in terms of schedule and cost, an important message after earlier delays linked to embargoes and localisation efforts.
From a tactical standpoint, Hızırreis substantially enhances the navy’s undersea capabilities. Its combination of fuel‑cell air‑independent propulsion (AIP) and large battery reserves enables the submarine to remain submerged for extended durations, ranging from several days to multiple weeks, without the need to raise a snorkel. This endurance significantly reduces vulnerability to satellite, radar, and electro‑optical surveillance, as well as to airborne and surface anti‑submarine warfare (ASW) assets. Open source reporting in Türkiye indicates that Piri Reis is engineered to operate at around 250 meters in routine missions, a depth range consistent with the Type 214 design. Although the Turkish Navy does not publish exact limits, widely cited estimates for the class place its maximum safe diving depth in the 300 to 400 meter band, depending on loadout and sea conditions. The submarine maintains a very low acoustic profile at these depths, using a quiet electric drive, fuel cell-based AIP, and a hydrodynamically refined hull that helps reduce flow noise during silent operations. These attributes make the vessel particularly effective for sustained intelligence, surveillance, and reconnaissance in heavily monitored choke points such as the Dardanelles and Bosphorus, and for discreet shadowing of surface groups in the Aegean, Eastern Mediterranean, and Black Sea.
Operationally, the Turkish Navy has already started to showcase Hızırreis alongside flagship surface units. The submarine took part on 24 August 2025 in the “Mavi Vatan Muhafızları Boğaz Geçişi” (Blue Homeland Guardians Bosphorus Passage) in Istanbul, sailing in company with the amphibious assault ship TCG Anadolu, the training ship TCG Savarona, the frigate TCG Oruçreis and other naval units. This type of public event underscores the role of the Reis-class as part of a broader “Blue Homeland” maritime posture, in which undersea assets are integrated with surface combatants, aviation and coastal defence systems to create layered deterrence from the Black Sea to the Eastern Mediterranean. When armed with Akya torpedoes and submarine-launched Atmaca, Hızırreis can threaten both surface combatants and high-value auxiliary vessels from standoff range; the planned integration of Gezgin would add a land-attack dimension, enabling simultaneous pressure on maritime and shore targets from a single platform. In this role, the submarine becomes a mobile, hard-to-detect launch node within a strike architecture that also includes surface ships, aircraft and land-based missiles.
The commissioning of Hızırreis alongside TCG Piri Reis equips the Turkish Navy with two operational AIP submarines, with four additional Reis-class vessels slated for delivery in the coming years, significantly enhancing regional deterrence in areas such as the Eastern Mediterranean, Aegean, and Black Sea. Initial program schedules targeted annual deliveries from 2022 to 2027, but delays due to sanctions and prioritization of domestic systems shifted TCG Piri Reis to August 2024 and Hızırreis to 2025; current progress indicates completion of the full class before decade's end, supporting modernization of aging Ay- and Preveze-class submarines. TKMS and Turkish officials project delivery of the third boat, TCG Muratreis, launched on 29 May 2025, approximately one year after Hızırreis, with sea trials commencing in early 2026.
For NATO, the Reis-class project strengthens the alliance’s indigenous AIP capabilities in the Black Sea and Eastern Mediterranean, reinforcing sea-denial and sea-control options vis-à-vis Russia’s submarine fleet and other regional actors. At the same time, the progressive technology transfer and experience accumulated through YTDP support Türkiye’s ambition to move towards a fully indigenous MILDEN-class submarine. Turkish media recalls that the first steel cut for the MILDEN programme took place in January 2025 at Gölcük, and that the project is being developed alongside the Reis line to capitalise on the workforce, infrastructure and know-how already in place. Turkish naval leadership has openly stated that, beyond MILDEN, the long-term goal is to acquire nuclear-powered submarines, positioning the Reis class as a bridge between conventional diesel-electric roots and a future nuclear undersea force.
The undersea portfolio does not end with large manned submarines. Leveraging experience from the Reis project, STM is advancing the construction of the STM500 mini-submarine, a smaller platform intended for special forces, coastal defence and export markets. In parallel, both STM and Aselsan are working on autonomous underwater vehicles sometimes described as “micro submarines”, such as STM-NETA and Aselsan’s Deringöz, which are designed for tasks ranging from reconnaissance to mine countermeasures and harbour security. Together, these programmes outline an ecosystem in which large AIP submarines like Hızırreis operate alongside manned mini-subs and unmanned underwater systems, giving the Turkish Navy a more flexible and layered presence beneath the surface.
The commissioning of TCG Hızırreis marks a significant milestone in Türkiye’s submarine modernization program, signaling a transition from planning to routine force generation and translating a complex binational industrial effort into tangible undersea capability. As the second Reis‑class submarine, Hızırreis strengthens the Turkish Navy’s resilience and versatility, expands options for deterrence and power projection, and sets the pace for the four remaining boats under construction. Against the backdrop of regional investments in advanced anti‑submarine warfare and new AIP platforms, the arrival of Hızırreis, alongside the ongoing build of Muratreis, the development of MILDEN, and emerging mini‑submarine and UUV projects, underscores that competition for influence in the Eastern Mediterranean and Black Sea is increasingly shifting to the undersea domain, where Türkiye is positioning itself as a sustained and capable presence.
Written by Teoman S. Nicanci – Defense Analyst, Army Recognition Group
Teoman S. Nicanci holds degrees in Political Science, Comparative and International Politics, and International Relations and Diplomacy from leading Belgian universities, with research focused on Russian strategic behavior, defense technology, and modern warfare. He is a defense analyst at Army Recognition, specializing in the global defense industry, military armament, and emerging defense technologies.