China is moving to develop improved warships. The 31 frigates of the various Jianghu sub-classes have been supplemented by a dozen improved frigates of the Jiangwei-I and -II classes. It is now thought that production of Jiangwei's will end when the 12th is complete, and a new class of frigates will enter production. As for destroyers, China completed two Luhi-class 4,600-ton destroyers but never built the rest of the announced class of six. Instead, production moved to the Luhai class, which tips the scales at 6,000 tons. Only one of these was built before the design evolved into the new Modified Luhai, which is thought to comprise a similar hull but with a very different weapons fit based on the Russian destroyers China has purchased. Two of these improved ships are under construction. All three Luhais use CODOG (Combined Operations, Diesel Or Gas) propulsion. Under such a system, the ships use fuel-efficient diesels most of the time, as their top speed of about 20 knots isn't an issue outside of combat. But when the shooting starts and the ships have to dash into attack range or out of trouble, they use Ukrainian-built gas turbines to push the top speed toward 30 knots.--Stephen V Cole