The first of a new class of air defence destroyer was laid down in 1942. It was to replace the older destroyers and take the Greenlandian destroyers into the post war period. Armament was to have three parts. The first was a dual purpose main gun system - but this would be fully automatic. The British and United States were working on a 3"/L70 automatic gun. Greenland decided that purchasing the rights to this gun would save a lot of time and effort producing their own automatic gun. Greenland would have liked a 90-105mm gun, but 76mm would have to do. When the designers worked out how much ammunition would be required to be stowed for the guns to be able to fire for a reasonable period of time, the figure was ginormous. If the ship was in action, firing its guns, for an hour, it would run out of shells very quickly. The only way to keep the ship in action past this time and until it could replenish ammunition, was to fit a few 40mm Bofors mountings. The second part was also dual purpose, these were two sets of triple Rocket Assisted Torpedoes (RATS) which could be used for both surface and sub-surface targets. The homing system in the torpedo would home in on the propeller cavitation noises, boom, blow off the stern of the ship. For submarine action the distance the torpedo could be fired on its rocket component could be altered to match the distance that the submarine was picked up by Asdic/Sonar. The third part was purely anti-submarine, with ahead throwing mortars mounted beside the bridge, tied to the Asdic/Sonar. Not unsurprisingly the ship grew and grew till it was almost light cruiser size.
Twelve ships were originally ordered, the Onyx in 1942, three more in the second half of 1943, four more in 1944 and a final four in 1945. Of those twelve ships only the first four were completed. Protracted problems with the autoloader system made them less than reliable. In the end the ships had cost more than twice the amount of the Jade class destroyer leaders which were of a size with the Onyx. The Onyx class were not considered good investments. With the 1950's, and the advent of missiles, the Onyx class were looked at to convert the aft end of the ships with a pair of medium range anti-aircraft missiles. This was never proceeded with and despite only being 15+ years old they were removed from the Navy list during the 1960's.
