Kortenaer-class

The Kortenaer class was developed as an anti-submarine warfare frigate for the Royal Netherlands Navy to replace the Holland and Friesland classes. Designed in the 1970s, the "Standard design" focused on NATO compatibility, allowing the platform to be adapted for anti-submarine or anti-aircraft roles. A total of 12 vessels were completed between 1975 and 1982, with construction split between the De Schelde and Wilton-Fijenoord shipyards.

The hull design featured a clipper bow, continuous upper and main decks, and a reduced length-to-beam ratio to improve stability in heavy seas. A combined gas or gas (COGOG) propulsion system provided separate turbines for cruising and high-speed operations. The engineering plant was distributed across four compartments and included auxiliary boilers and evaporators for redundancy. To reduce crew requirements, the class incorporated high levels of automation, enabling the ship to be operated from the operations room. Sensor systems consisted of air search, surface search, and fire control radars, complemented by bow-mounted or towed array sonar and a SEWACO II action data system. Armament as built included a forward naval gun, anti-ship missiles, anti-aircraft missiles, and torpedo tubes. The stern housed a flight deck and hangar for helicopter operations.

The Royal Netherlands Navy originally intended to commission all 12 units, but sold two to Greece while they were still under construction. These were replaced in the Dutch program by the Jacob van Heemskerck class, an air defense variant. In Dutch service, the class initially conducted Atlantic Ocean patrols. During the 1990s, their mission profile shifted to the Mediterranean Sea and the Persian Gulf, where they participated in NATO blockade operations during the Yugoslav Wars and supported the Gulf War. Further deployments included the United Nations blockade of Haiti in 1993 and participation in Operation Enduring Freedom in 2001.

Between 1992 and 2003, the Royal Netherlands Navy retired the class and transferred the remaining eight vessels to the Hellenic Navy. These joined the two units acquired during construction, which the Greeks designated as the Elli class. Greek variants featured modifications including lengthened hangars to accommodate different helicopter types and the installation of alternative close-in weapon systems. Two additional ships were sold to the United Arab Emirates in 1996. These vessels were refitted with enhanced air conditioning and updated radar systems for Middle Eastern operations. One UAE vessel, Al Emirat, was subsequently converted into the civilian yacht Yas. An earlier contract for eight vessels intended for the Imperial Iranian Navy was cancelled following the 1979 Iranian Revolution.