How a specialized submarine hunter evolved into a versatile warfare backbone

Countries & Cities · Published 12 October 2026 · Updated 25 October 2026 Swipe more like this →

In short: Designed in the late 1970s to hunt Soviet nuclear submarines in the North Atlantic, the Type 23 frigate has become much more than a specialist. Through decades of combat lessons and technological shifts, these vessels have transformed from quiet hunters into complex, multi-role warships.

The Type 23, or Duke class, was originally conceived as a light anti-submarine frigate. Its primary mission was to counter Soviet nuclear submarines using advanced towed-array sonar. To achieve the necessary stealth, the ships utilized a combined diesel-electric and gas (CODLAG) propulsion system, which allows for exceptionally quiet running during anti-submarine operations.

The Falklands War fundamentally altered the class's trajectory. Initially designed without an anti-air warfare system, the conflict necessitated the introduction of the Sea Wolf missile. This evolution turned the Type 23 into a more balanced vessel, integrating Harpoon surface-to-surface missiles and medium-calibre guns for naval gunfire support. This transformation required significant technological updates, including the replacement of older radar systems with the BAE Systems Type 997 Artisan 3D radar, which is reportedly five times more capable than its predecessor.

The class has faced significant logistical and financial shifts over its lifespan. While early estimates in 1980 placed the cost at £75 million per ship, the complexities added by combat lessons increased that figure. By 2001, the Ministry of Defence reported HMS Norfolk cost £135.449 million, while later vessels were expected to cost between £60 million and £96 million. As the Royal Navy prepares for the next generation, the Type 23 is being phased out. The Type 26 and Type 31 classes are slated to replace them, with HMS St Albans anticipated to be the final vessel to retire in 2035.

The fleet's composition is also shifting through international sales. While the Royal Navy has seen eight ships retired since 2021, three Type 23 vessels have been sold to the Chilean Navy, which has also procured Sonar 2087 towed arrays from Thales Underwater Systems.

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