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H-029-2: The EC-121 “Deep Sea 129” Shootdown

A U.S. Navy Lockheed EC-121K Warning Star (BuNo 141292) from electronic warfare squadron VAQ-33 Firebirds in formation with a Douglas EA-4F Skyhawk and a McDonnell F-4B Phantom II off the coast of Virginia (USA) in April 1973.
A sister aircraft to "Deep Sea 129": A U.S. Navy Lockheed EC-121K from VAQ-33 "Firebirds" in formation with a Douglas EA-4F Skyhawk and a McDonnell F-4B Phantom II off the coast of Virginia, April 1973 (Naval Historical Center).

H-Gram 029, Attachment 2

Samuel J. Cox, Director NHHC

April 2019

(Before anyone panics, all discussions of communications intelligence are sourced from the National Security Agency’s declassified and redacted “The National Security Agency and the EC-121 Shootdown,” United States Cryptologic History, Crisis Collection Vol. 3. Office of Archives and History NSA/CSS, originally produced in 1989 in classified form, which can be found on NSA’s website.)

On 28 March 1969, two North Korean Mig-21 Fishbed F fighters (North Korea’s latest and greatest) of the 1st Fighter Division deployed from their home airfield of Pukchang-ni to Hoemun Airfield, site of the North Korean Air Force Air School’s jet training element, on the east coast of North Korea. This flight was detected by U.S. national intelligence sources and was noted as the first time Fishbeds had deployed to Hoemun, and therefore unusual. This deployment was not known to the crew of the EC-121 on the ill-fated 15 April 1969 mission, although it probably wouldn’t have made any difference as the deployment was assessed to be “training related.” A U.S. Navy EC-121M intelligence collection aircraft, call sign “Deep Sea 129,” would be shot down in international airspace off the coast of North Korea by one of these two aircraft.

The EC-121 Warning Star was a modified Lockheed Super Constellation, a four-engine passenger airliner in wide use for long-range air travel until the advent of the much faster Boeing 707 and Douglas DC-8 jet passenger airliners. The military variant, which served in both the U.S. Navy and Air Force, was originally designed as an airborne early warning platform to supplement the Distant Early Warning (DEW) Line, which guarded against Soviet bombers crossing over the north polar region. The aircraft was introduced in the U.S. Navy in 1954, with 142 being procured, and originally designated WV1, WV2, and WV3 (based on variant), and nicknamed “Willie Victors” before being designated as EC-121 in the late 1950s. Most of the AEW variants were out of service by 1965, although a number were converted to a “Batcat” configuration and used to monitor sensors emplaced along North Vietnamese supply and infiltration routes into South Vietnam during the Vietnam War. All but one of the Navy EC-121s was out of service by 1978. During the service life of the aircraft, 20 were destroyed in accidents with a total loss of 113 air crew.

In the late 1950’s, 13 WV-2 variants were converted to EC-121M electronic and communications intelligence collection configuration (and another nine were converted to weather reconnaissance “hurricane hunter” configuration). The EC-121M had a large radome on top to collect target radar signals and antennae on the underside to collect communications signals. Loaded down with about six tons of electronic equipment, the EC-121M only had a top speed of about 220 knots and maximum altitude of 20,000 feet. Normal crew complement was in the range of 10 to 15 personnel depending on the mission. Unlike previous aircraft used for intelligence collection missions, such as the P-2V Neptune, the EC-121 was unarmed and it did not have any defensive electronic countermeasures (DECM) capability to jam threat radars.

In the western Pacific, EC-121M’s were flown by Fleet Air Reconnaissance Squadron ONE (VQ-1) based at Naval Air Station Atsugi, Japan (VQ-1 also flew the EA-3B “Whale” carrier-based intelligence collection aircraft). Specialized intelligence collection personnel that flew on the aircraft were stationed nearby at Naval Security Group Activity, Kamiseya (USN-39).

The primary purpose of the Navy’s EC-121M was “fleet support,” and the Navy, with some degree of reluctance, allocated flights to participate in the Peacetime Aerial Reconnaissance Program (PARPRO) in effect since the early 1950s. PARPRO flights used service assets to conduct stand-off (i.e., in international airspace) intelligence collection against “denied area” countries such as the Soviet Union, People’s Republic of China, and the Democratic People’s Republic of Korea (North Korea) to obtain Intelligence of national significance. Those PARPRO missions that included communications intelligence (COMINT) were tasked by the National Security Agency (NSA), which by then had consolidated control of all U.S. COMINT activity. Electronic Intelligence (ELINT), which then mostly consisted of identifying and monitoring radar activity, was still pretty balkanized among the services and national intelligence agencies (and to a lesser degree still is).

Navy PARPRO flights by EC-121Ms were termed by the Navy to be “Beggar Shadow,” to the consternation of NSA, as Beggar Shadow connoted a nationally tasked and controlled (by NSA) mission for the primary purpose of COMINT collection. NSA’s objection was that Navy EC-121M Beggar Shadow flights were not tasked by them or under their control, but were rather Navy missions to meet fleet requirements (vice national requirements) under Navy operational control, in this case of Commander U.S. Seventh Fleet. At the time, it was anathema to the Navy for any assets to be “controlled” by any agency outside the Navy.

The Navy’s desire for “independence” (NSA’s view), as well as shortage of funding, was such that Navy aircraft lacked the equipment to participant in an advisory warning system set up by NSA for reconnaissance aircraft, which by then had become standard on USAF intelligence collection aircraft as a result of the near-shootdown of a USAF ERB-47H in international airspace off eastern North Korea in 1965. The lack of this system would make it impossible to verify whether Deep Sea 129 received any of the warning messages sent prior to the shootdown, and would result in a serious delay in initiation of search-and-rescue operations (which, however, would have been fruitless, but that was certainly not known at the time.) The difference between “nationally tasked” and “service tasked” PARPRO missions still sometimes results in confusion even today.

The process of determining a threat assessment for EC-121M missions flown against North Korea was as flawed as that for the USS Pueblo (AGER-2) before she was captured by the North Koreans in January 1968. Despite being termed Beggar Shadow, the missions were not tasked by NSA and NSA did not participate in the threat assessment process, which was the responsibility of the U.S. Navy. Both Pacific Fleet and Seventh Fleet determined that the missions against North Korea were “minimal” threat, because numerous Navy and Air Force missions had been flown since 1965 with no incident. Despite the capture of the Pueblo, there was a completely unjustified assumption that the North Koreans would respect international airspace (North Korea claimed 12 nautical miles at the time, at least officially). Numerous USAF missions had flown without being attacked, and the Navy had flown 14 EC-121M Beggar Shadow flights against North Korea since November 1968, at a rate of about two to three per month, also without incident.

Nevertheless, a history of North Korean hostile responses to reconnaissance and intelligence collection flights would suggest more concern was warranted. Very shortly after the armistice was signed in 1953, North Korea shot down a U.S. Army L-20 Beaver observation aircraft near the Demilitarized Zone (DMZ) on the Korean peninsula on 19 January 1955. On 16 June 1959, two North Korean Mig-17 Fresco fighters attacked a U.S. Navy VQ-1 P4M-1Q Mercator flying an electronic intelligence collection mission 50 nautical miles east of Korea over the Sea of Japan. The two MiGs made multiple firing passes with guns. The Mercator’s starboard engine was badly damaged and the tail gunner wounded, but the aircraft was able to escape by diving right to below 50 feet above sea level and eventually making a forced landing in Japan. (The Martin Mercator was a competitor to Lockheed P-2V Neptune ASW aircraft, originally conceived during World War II as a high-speed minelaying aircraft for the invasion of Japan. Although it was 100 knots faster than the P2V, it was much larger, heavier, and much more difficult to maintain. The Navy only procured 19 of them, eventually converting 18 of them to an electronic intelligence collection configuration.) Then, on 27 April 1965 a USAF ERB-47H Stratojet, subordinate to the 55th Strategic Reconnaissance Wing, was attacked by two North Korean MiG-17’s with guns over the Sea of Japan, 80 nautical miles off the east coast of North Korea. The aircraft was badly shot up, with major structural damage and loss of two turbojet engines (of six), although the tail gunner shot down one of the MiG-17s, but was able to make an emergency landing at Yokota (some sources do not mention, or do not confirm, the shootdown of the MiG).

The geopolitical-military situation on the Korean Peninsula was cause for significant concern as well. With the U.S. deeply engaged in the war in Vietnam, North Korean dictator Kim Il-Song thought that would be an opportune time to drastically increase the number of provocations and firing incidents along the DMZ, which resulted in the deaths of 43 U.S. soldiers, 299 South Korean soldiers and about 400 North Korean soldiers over the next three years, while at the same time tripling North Korea’s defense budget, and obtaining newer, more capable weapons, such as Mig-21 fighters. In January 1967, North Korean coastal artillery sank the South Korean patrol boat ROKS Dangpo (PCEC 56) (ex–USS Marfa) near the DMZ killing 39 of 79 crewmen.

Well over a thousand armed North Korean agents infiltrated into South Korea during this period, including a 31-man detachment infiltrated into Seoul on 21 January 1968 in an almost-successful attempt to assassinate the South Korean president. This “Blue House Raid” resulted in a running gun battle in the streets of the city in which 3 U.S. soldiers and 26 South Koreans were killed, along with 28 of the North Korean team (plus one captured and two unaccounted for). This raid was followed by the brazen attack on, and capture of, the U.S. intelligence collection ship USS Pueblo (AGER-2). It was also noted that the usual din of North Korean belligerent rhetoric increased significantly in 1969 (which was briefed to Deep Sea 129’s crew as an item of concern). During the 1968 election campaign, Richard Nixon had dismissed North Korea as a “fourth rate” military, but that under-estimation appeared prevalent in senior levels of the U.S. military as well.

Deep Sea 129 took off from Naval Air Station Atsugi, Japan at 0700 local on Tuesday 15 April (2200Z on 14 April) for a “Beggar Shadow” electronic reconnaissance mission off the east coast of North Korea, with orders to approach no closer than 50 nautical miles, and with the intent to recover at Osan Air Base, South Korea. Under the command of Lieutenant Commander James H. Overstreet, the aircraft had 31 crewmen aboard—8 officers and 23 enlisted, significantly more crewmen than was required for the mission (normally between 10 and 15 were carried). The extra crewmen were trainees who would get the bonus of liberty in South Korea. Among the crew were ten aviation electronics technicians and nine cryptologic technicians (including one Marine). Scheduled for an eight-and-a-half-hour mission, Deep Sea 129 was to fly to a point near the North Korean/Manchurian (PRC) border (no closer than 50 nautical miles) and then fly two and a half orbits along a 120–nautical mile elliptical track parallel to the east coast of North Korea.

At 1330 local (0430Z), the two North Korean MiG-21s that had been deployed to Hoemun launched. The launch was timed so that the MiGs would have the shortest time of flight to intercept Deep Sea 129’s track, a track that by then the North Koreans were completely familiar with, and indicating the event was planned. Initial reflections of the launch were detected by U.S. signals intelligence (SIGINT) assets at 1335 local (0435Z.) One of the MiGs set up an overwater defensive patrol (DEFPAT) approaching no closer than 65 nautical miles to Deep Sea 129, while the other MiG continued directly toward Deep Sea 129 and, at 1338 (0438Z), was noted within 50 nautical miles of the EC-121 and closing fast. Warning was issued by U.S. SIGINT sites, but it is unknown if Deep Sea 129 received it. At 1344 (0444Z), SIGINT and radar reflections of the two tracks merged and the shootdown probably occurred at 1347 (0447Z) by one, possibly two, AA-2 Atoll infrared-seeking air-to-air missiles (Soviet version of AIM-9 Sidewinder) fired by the MiG-21 in a position approximately 80 nautical miles from the North Korean coast. (Of note, previous attacks had been with guns.)

Standard procedure for an EC-121 under threat was to dive toward the deck, so when Deep Sea 121 disappeared from radar at 1251 (0451Z), it did not necessarily mean it had been shot down, so there was a significant period of uncertainty amongst radar and SIGINT sites in South Korea and Japan about what happened. There was no message from Deep Sea 129 indicating it was under attack. Nevertheless, at 1345 (0445Z), in response to the North Korean reaction to Deep Sea 129, the U.S. Air Force commanding general at Osan Air Base had ordered the launch of two F-102 fighters to take a combat air patrol (CAP) station in a position 140 nautical miles off the South Korean coast along Deep Sea 129’s planned track, about 100 nautical miles south of the incident location. The two aircraft actually launched at 1404 (0504Z) to await the arrival of Deep Sea 129 or to assist if the aircraft was in trouble, but by then it was already too late.

At 1400 (0500Z,) NSGA Kamiseya (USN-39) made a normal hourly comms check, except this time there was no answer from Deep Sea 129. This was the first indication USN-39 had that something was wrong. (Of note, the NSA history differs significantly from what was in press reports at the time or in Wikipedia and other sources now.) Due to a message addee issue, which was a byproduct of the Navy not having the newer NSA threat advisory system, USN-39 did not receive three warning messages, and it is uncertain whether Deep Sea 129 did either (this also differs significantly from press reporting). The U.S. Fifth Air Force in Japan was also unaware, and was alerted only after querying Osan why CAP had been launched.

Concern over Deep Sea 129 began to mount when after about ten minutes after disappearing from radar, Deep Sea 129 neither re-emerged nor communicated. Even so, it was not until 1444 (0544) that a U.S. SIGINT site issued a CRITIC message (essentially a flash override message in NSA comms channels) to NSA indicating the aircraft might have been shot down. At 0558Z (middle of the night DC time), NSA lateralled the CRITIC to the White House, and other key JCS and service watch centers. Only when USN-39 was finally notified was a search-and-rescue (SAR) effort commenced, almost an hour after the event, at which time an HC-130 was launched from South Korea with F-106 fighters as protection.

At 1555 Korea time (0655), the U.S. Foreign Broadcast Information Service (FBIS) monitoring North Korean radio broadcasts noted that North Korea announced that a U.S. aircraft had been shot down (with a “single shot”) at 1350 (0450Z) after intruding deep into North Korean airspace. North Korea lauded the attack as a “brilliant achievement” and warned that retaliation would be met with “hundredfold revenge.”

Upon learning of the missing aircraft, the commander of U.S. Seventh Fleet, Vice Admiral William F. Bringle, embarked on USS Oklahoma City (CLG-5), directed the destroyer leader USS Dale (DLG-19, later CG-19) and destroyer USS Henry W. Tucker (DD-875) to get underway from Sasebo, Japan, to conduct a SAR. Meanwhile, at a very high government-to-government level, the U.S. requested Soviet assistance for the SAR, and two Soviet destroyers, the Kotlin-class Vodokhnovenny (DD-429) and DD-580 promptly responded and arrived in the area. The first debris were spotted the next morning by a P-3 Orion, and the Soviet destroyers began picking up debris. Dale and Tucker arrived later that afternoon and also began picking up debris. On 17 April, Tucker located and retrieved the bodies of two crewmen, the only ones found. The Soviets also granted permission for U.S. aircraft to overfly their ships to take photos of debris on deck. On 18 April, Tucker rendezvoused with Vodokhnovenny and cross-decked debris from the Russian destroyer. Subsequent analysis of recovered debris indicated shrapnel perforation consistent with at least one air-to-air missile like the AA-2 Atoll carried by the Mig-21s.

In anticipation of national direction, the commander in chief, U.S. Pacific Command, Admiral John S. McCain, Jr. (whose son was a prisoner of war in North Vietnam), ordered the activation of Task Force 71 at 0342Z on 16 April, consisting of three attack carrier strike groups centered on the nuclear carrier USS Enterprise (CVAN-65), which had recently completed repairs from her serious fire in January 1969 (see H-Gram 025), in company with the reactivated battleship New Jersey (BB-62), Ticonderoga (CVA-14), and Ranger (CVA-61). In addition, TF-71 included an ASW carrier group centered on Hornet (CVS-12), and an air defense group led by Chicago (CG-11), a surface action group including Oklahoma City (CLG-5) and the heavy cruiser Saint Paul (CA-73), and numerous other escorting destroyers and support ships.

Although President Nixon had declared that there would be “no more Pueblos,” he found himself in much the same quandary as President Johnson when Pueblo was seized—with no good options. The National Security Council met on 16 April and split between those favoring aggressive military action and those favoring a more cautious diplomatic approach. Nixon also received conflicting advice from key senators. Although Nixon and National Security Advisor Henry Kissinger favored more aggressive action, with public and political support for the war in Vietnam dropping rapidly, the last thing Nixon needed was another war. Some in the media would claim that the shootdown was an accident, or at least there was no proof it was deliberate. As tragic as the shootdown was, it should also be noted that in 1969 the U.S. was losing over 500 servicemen killed every month in Vietnam. Also, although North Korean rhetoric was as bellicose as ever, all indications after the shootdown were that North Korea military actions were defensive in nature and there were no signs of an imminent North Korean offensive. And, there was always the problem that South Korean capital of Seoul, with millions of civilians, was hostage to North Korean rocket and artillery fire, and the realization that any war on the Korean peninsula would be a bloody affair.

After much deliberation, Nixon opted only to send TF-71 into the Sea of Japan as a massive show of military force, and to resume intelligence collection flights against North Korea within a week to demonstrate that the U.S. would not be intimidated. Nixon finally addressed the American public on 18 April, during which he revealed detailed intelligence information that NSA at least wished he hadn’t. Nixon promised that the North Koreans would “never get away with it again.”

Although the U.S. Navy units that entered the Sea of Japan engaged in substantial planning to achieve air superiority over North Korea, using aircraft and/or surface-to-air missiles, and bomb key targets, or to initiate a blockade (or some combination thereof), it all came to naught. Although Soviet naval units continually shadowed the U.S. Navy forces, there was no reaction by the North Korean Navy. By 26 April, TF-71 units began to depart, mostly to resume combat operations off Vietnam. By 1 May, only the destroyer leader Sterrett (DLG-31, later CG-31) and destroyer Rowan (DD-782) remained off the east coast of Korea.

 Vice Admiral Bringle directed that a Naval board of inquiry be convened, which it did at Atsugi commencing 20 April 1969. After extensive deliberation the board came up with two primary recommendations. The first was to overhaul the process for determining threat levels and for providing timely warning to reconnaissance and intelligence collection aircraft. The second recommendation was for the Navy to procure a better aircraft than the EC-121. (The program for the EP-3E Aries I was already underway, with the first of 12 aircraft delivered in 1969, although the recommendation also sparked a comparatively brief flurry of interest in using drones to conduct intelligence collection, which would be resurrected two decades later.) A special subcommittee of the House Armed Services Committee, charged with investigating the incident was quite critical of the command and control of the missions (especially by the Navy; the NSA study is also extremely critical of the Navy).

The tragedy of Deep Sea 129 did lead to significant improvements in how Navy PARPRO missions were approved, tasked, briefed, and supported. Although there were numerous intercepts of U.S. Navy intelligence collection flights since the shootdown of Deep Sea 129, none were fired on or lost until 1 April 2001, when a Peoples Liberation Army Naval Air Force (PLANF) J-8 Finback II fighter collided with an EP-3E Aries II of VQ-1 in mid-air after conducting dangerous maneuvers during an intercept off Hainan Island, China. The PRC pilot ejected from his damaged jet, but was never found. The seriously damaged EP-3E with 24 crewmen aboard made an emergency landing at Lingshui (a PRC fighter base on Hainan Island). The crew was returned to the United States on 11 April, and the disassembled aircraft returned in July, after the Chinese no doubt gained everything of intelligence value they could from it.

As to what it was the North Koreans learned from the shootdown of Deep Sea 129, it was that “they will never get away with it again” was mostly meaningless U.S. rhetoric, although for the most part, the North Koreans limited their periodic outrages at the South Koreans rather than the United States. An exception was the killing of two U.S. soldiers by North Korean soldiers in an attack known as the “Axe Murder Incident” on 18 August 1976. It didn’t take long before the North Koreans were at it again, when in December 1969, North Korean agents hijacked a Korean Air YS-11 to Pyongyang, returning only 39 of the 46 passengers and 4 crew. Beginning in 1974, the first of four infiltration tunnels that the North Koreans had dug under the DMZ were discovered, each capable of moving a regiment per hour, including heavy artillery, into the rear of South Korean forces. (North Korea claimed they were abandoned coal mines—I’ve been in one, not a chance it’s a coal mine.)

North Korean provocations intensified again in the 1980s prior to the 1988 Seoul Olympics. In October 1983, North Korean agents narrowly missed assassinating South Korean President Chun Doo-hwan with a command-detonated bomb in Rangoon, Burma; the bomb failed because the president was delayed in traffic and the South Korean version of “Hail to the Chief” was played prematurely. The bomb killed 21 and injured 46. Among the dead were four senior South Korean cabinet ministers, including the foreign minister, and 14 other South Koreans. In September 1986, North Korea agents set off a bomb in South Korea’s Gimpo International Airport, killing five. In November 1987, North Korean agents planted a bomb on Korean Air Lines flight 858, which detonated over the Andaman Sea, killing all 115 aboard.

On 15 September 1996, a North Korean Sang-o midget submarined ran hard aground in South Korean waters after putting a three-man reconnaissance team ashore on the country’s east coast. The rest of the reconnaissance team (wearing South Korean uniforms) first executed the 11-man crew of the submarine and then went ashore, resulting in a 49-day manhunt, during which 13 North Korean infiltrators and 8 South Korean soldiers were killed in firefights (and 4 more South Korean soldiers in accidents). Only one North Korean infiltrator is believed to have made it to North Korea. The Sang-o is now up on blocks in a park on the east coast of South Korea (I’ve been inside that, too). On 22 June 1998, a North Korean Yugo-class midget submarine was exfiltrating North Korean agents from South Korea when it became entangled in fishing nets in South Korean waters. While being towed by a South Korean corvette, the four North Korean agents executed the five submarine crewmen and then committed suicide, and the submarine sank, but was subsequently raised by the South Koreans. In December 1998, South Korean navy vessels sank a North Korean I-SILC semi-submersible just west of Chinhae.

Between 1997 and 2002, there were multiple skirmishes between the North and South Korean navies along the Northern Limit Line off the west coast of South Korea, including the First Battle of Yeonpyeong in 1999 (one North Korean torpedo boat sunk with 17 to 30 KIA and three patrol boats severely damaged) and the Second Battle of Yeonpyeong in 2002 (one ROKN patrol boat sunk with six KIA and one North Korean patrol boast severely damaged with 13 KIA). This was followed by the Battle of Daechong in 2009, in which one North Korean patrol boat was damaged with eight KIA. The series of naval engagements culminated on 26 March 2010, when a North Korean Yono-class midget submarine sank the ROKN corvette Cheonan with a wake-homing torpedo in a surprise attack in South Korean territorial waters, killing 46 of Cheonan’s crew (58 were rescued). The United Nations condemned the attack without naming North Korea as being responsible. (I led the international multi-national intelligence team in Seoul assisting with the South Korean investigation—a future H-gram). It’s been almost ten years since the Cheonan sinking, and, like the Mercator incident in 1959, most people have forgotten, so we are probably overdue for another example of North Korean bad behavior.

Sources consulted: For the EC-121 section, the primary source is the recently (2015) released National Security Agency’s declassified and redacted “The National Security Agency and the EC-121 Shootdown,” United States Cryptologic History, Crisis Collection Vol 3., Office of Archives and History NSA/CSS, originally produced in classified form in 1989, and which can be found on NSA’s website. Other sources include: “By Any Means Necessary: America’s Secret Air War in the Cold War,” William E. Burrows, 2003. “The EC-121 Shoot Down and North Korea’s Coercive Theory of Victory” by Van Jackson 13 April 2017, at “Lessons from the Capture of the USS PUEBLO and the Shootdown of a U.S. Navy EC-121, 1968–1969” by Richard A. Mobley, Studies in Intelligence, Vol. 59, No 1., 2015. There are a number of lists of aircraft shot down during the Cold War of varying degrees of accuracy. Although the site by David Lednicer ( does not appear to have been maintained for a while, it is the most comprehensive list I have found, and my spot checks of research indicates it is very thorough and accurate.

Back to H-Gram 029 Overview 

Published: Fri May 03 15:08:28 EDT 2019