The Anzac class (also identified as the ANZAC class and the MEKO 200 ANZ type) is a ship class of ten frigates; eight operated by the Royal Australian Navy (RAN) and two operated by the Royal New Zealand Navy (RNZN). During the 1980s, the RAN began plans to replace the River class destroyer escorts with a mid-capability patrol frigate, and settled on the idea of modifying a proven foreign design for Australian conditions. Around the same time, the RNZN was seeking to replace their Leander class frigates while maintaining blue-water capabilities. A souring of relations between New Zealand and the United States of America in relation to New Zealand's nuclear-free zone and the ANZUS security treaty prompted New Zealand to seek improved ties with other nations, particularly Australia. As both