In late March 1972, the North Vietnamese undertook an invasion of South Vietnam, rolling armor and troops across the DMZ. As part of a response to the invasion, US Navy ships were assigned to provide gunfire support along the coast of Vietnam. As part of that operation, on April 19, 1972, a group of US Navy ships were lining up for a gunfire mission off the coast of North Vietnam near Dong Hoi. As is recounted by Elden G. Miller here one of the ships was the USS Sterett (DLG-31):
On April 19, Sterett was at her normal station in the northern part of the Gulf of Tonkin and received orders to head south and provide anti-air support for a gun-line mission near Dong Hoi, just north of the demilitarized zone (DMZ) near Dong Hoi. Prior to April 19, air strikes had reportedly softened up the area and intelligence sources suggested that no viable enemy aircraft remained in the area.
Sterett rendezvoused with the light cruiser Oklahoma City (CLG-5), the destroyer Higbee (DD-806) and destroyer Lloyd Thomas (DD-764). Sterett launched her LAMPS helicopter, to operate as an airborne spotter for the gunfire mission.
At 1600 Oklahoma City, Higbee and Lloyd Thomas began their gun run against targets in the vicinity of Dong Hoi. The first pass was from north to south, parallel to the coast with a return leg back towards the north. Upon commencing their run, all three ships started to receive heavy counter fire from shore batteries. No hits were experienced on Oklahoma City, Higbee or Lloyd Thomas but many shells appeared to bracket the ships. Oklahoma City reported shrapnel damage to her superstructure from some of the near hits.
Also shortly after the task group arrived off shore, several air targets were detected amongst the mountains. A single MiG 17 came out of the mountains and headed for the USS Higbee and dropped a single 250 pound bomb. It was a near miss with no damage.
Sterett had two missiles on the rails and a single Terrier missile was launched towards the MiG and missed. Sterett then fired the remaining missile and downed the MiG.
Higbee had experienced a hot round in her "Mount 52" after gun mount and the mount had been evacuated just prior to the MiG's second pass which resulted in a single 250-pound bomb hitting at the base of the vacated 5-inch gun mount. The bomb penetrated the weather deck and caused the ready ammunition stored below to explode and destroy the gun mount. Higbee experienced only four injuries and no loss of life.
After the first MiG started it’s first bomb run, a second MiG exited the mountains and executed a 180-degree turn and headed back into the mountains. Sterett fired two missiles at this MiG and assumed a "kill" when the missile and plane disapeared from radar simultaneously.
Higbee, Oklahoma City and Lloyd Thomas exited the area to the northeast, accompanied by the Sterett. Sterett was roughly paralleling Higbee’s course and making oblique course changes as they headed away from the battle area to keep Sterett's forward missile main battery unmasked.Sterett was tracking a couple of small high-speed surface tracks during this exit. As they were observing one of the tracks vertical video separation was noted. At the same time Sterett detected an electronic signature identified as a Russian SS-N-2 Styx missile. Sterett immediately fired a salvo of two Terrier missiles at the suspected Styx missile. Following the detonation of Sterett's Terrier, the missile target disappeared from radar and the ECM signature signal ceased signifying a kill.
Sterett’s gun crews had so far been mere spectators during the action that day. Two surface targets were paralleling Sterett's course and speed. The Sterett’s aft mounted 5" 54 mount made short work of the surface targets and they to disappeared from radar...
Some you might not be familiar with the Styx missile, but it has recently been known in the Chinese version as the "Silkworm":
China acquired the Russian SS-N-2 Styx missile technology in 1959, and production began in 1974. The Russian SS-N-2 was used in 1967 against Israel by Egypt, in 1971 by India against Pakistan, and by Iran during its 1980-88 war with Iraq. Chinese copies of the Styx design (CSS-C-2 Silkworm and CSS-C-3 Seersucker) coastal defence missiles and the ship launched CSS-N-1 and CSS-N-2 were used by both sides in the Iraq-Iran War(source)
Technological improvements to the C-801/SARDINE and the C-802/ SACCADE are providing a gradual upgrade to China's current force of antiquated first generation CSS-N-1 SCRUBBRUSH ASCMs. It was reported in 1996 that Iran had begun indigenous production of a medium-range antiship missile, the FL-10, based on the Chinese FL-2 or FL7 and developed with Chinese technical assistance.
An analysis of the Battle off Dong Hai, by Stuart Slade, concerning the Styx incident is here. Mr. Slade first sets out a USS Sterett account:
Sterett's fire control radar operators had locked onto several of the surface tracks in CBT mode (Continuous Boat Track). As they were observing one of the tracks, they detected vertical video separation. The radar automatically maintained its lock onto the video that separated from the surface target. At the same time Sterett's ECM (Electronic Counter Measures) crew in CIC (Combat Information Center) received an electronic signature of an ASCM (Anti Ship Cruise Missile) and the fire control radar associated with a missile launch. It was immediately identified as a Russian SS-N-2 Styx missileThen Mr. Slade goes on to discount the idea that the Sterett was ever fired upon by a missile:
This was the first time a Navy ship had been attacked with a guided missile in a combat situation. The positive lock by the SPG-55 fire control radar allowed Sterett to fire a salvo of two Terrier missiles immediately following the Styx launch. If Sterett would have had to acquire the Styx normally with her air search radars, plot the course via several paints (radar sweeps) and then hand it over to the missile fire control radars, she could never have fired missiles in time to intercept the Styx missile. Bridge lookouts reported seeing Sterett's Terriers enter a cloudbank and explode. The Styx was never visually spotted. Following the detonation of our Terrier, the missile target disappeared from radar and the ECM signature signal ceased...
I don't believe there ever was a missile launch at Sterett, although the CIC crew had every reason to believe that there had been one and they acted entirely correctly. I think we had a combination of a very confused radar environment made worse by the use of an unsuitable radar for surface search and a misinterpretation of the available data. I don't rule out the possibility of an inbound P-15 completely, but the more I look at the situation, the less likely it seems. I think the USN had good reason to disallow the claimed shoot-down. This does not change the fact that the CIC crew did a fantastic job in a very confused environment. They had an air action to fight, a crippled ship to protect and also a potentially lethal surface threat developing. Even if they didn't kill a missile, they still deserve a salute for jobs well and skillfully done.