Donghae-class

The Donghae-class patrol combat corvette was developed under the Republic of Korea Navy’s 1st Yulgok Project (1974–1986). The class was intended to provide a domestic, cost-efficient complement to the Ulsan-class frigate, replacing ex-US World War II vessels that were nearing retirement. Designers selected a U-shape hull to prioritize ship stability at patrol speeds, bypassing V-shape designs that would have required fin stabilizers. Propulsion requirements shifted during the planning phase from a combined diesel and diesel (CODAD) system to a combined diesel or gas (CODOG) configuration to achieve higher speeds. During sea trials, the lead ship underwent propeller modifications to address acoustic issues that affected anti-submarine operations.

The class is designed for littoral defense, maritime border patrol, and surface combat against small vessels. It utilizes a CODOG propulsion system consisting of a gas turbine and diesel engines. The sensor suite includes surface-search and fire-control radars, a sonar system, and an optronic director. For anti-submarine missions, the ships are equipped with torpedo tubes and depth charges. Because of budget limitations during the development period, the class lacks air-search radar and dedicated anti-air weaponry, instead utilizing electronic support measures and decoys for self-defense. Subsequent design changes, including a shift to a V-shape hull, led to the development of the succeeding Pohang-class.

Four units were commissioned into the Republic of Korea Navy in 1983: Donghae, Suwon, Gangneung, and Anyang. These vessels were primarily deployed to protect the littoral zone and patrol the Northern Limit Line. In December 1998, ROKS Donghae participated in the sinking of a North Korean semi-submarine near Yeosu. In 1990, the secondary armament was upgraded to allow for night operations and integration with the fire control system. The Republic of Korea Navy began retiring the class in 2009 to be replaced by the FFX program. ROKS Anyang was transferred to the Colombian Navy in 2013. Following a refurbishment that included the modification of its gun systems, the vessel was commissioned as ARC Nariño, which remains in active service.