THEY SERVED IN SILENCE

The Story of a Cryptologic Service and Sacrifice

Vanguard 216

CPT Michael W. Marker, WO1 Harold L. Algaard, 

SP5 Richard J. Hentz, SP5 Rodney D. Osborne

SP6 John T. Strawn

“I was scheduled to fly on that aircraft. I had previous Morse and DF experience. That morning, I was just 

climbing in, when someone came running up to the plane and told me that I had been bumped. SP6 John T. 

Strawn jumped on in my place. My duty assignment as briefing team chief just took priority over this mission.... 

SP6 Strawn and the rest of the crew took off shortly thereafter and they never landed.”

 CW2 Joseph Hayes

Since the earliest days of the Vietnam War, the Army Security Agency had provided and protected critical 

cryptologic-related intelligence in a combat support role. By the mid-’60s, the organization had developed 

several innovative practices in their work. One of the most effective was the implementation of airborne radio 

direction finding and collection. As part of this initiative, the 138th Army Security Agency Company (Aviation) was 

stood up and activated at Da Nang, South Vietnam in June of 1966. From the beginning, the unit had a reputation 

for providing critical intelligence not only to US Army components, but Marine Corps units as well. 

Utilizing a variety of aircraft, ASA crews, flown by 138th pilots, used a combination of innovative methods and 

state-of-the-art technology to locate enemy units. Once located, gunships could then be directed by them 

to the area to bring firepower to bear. By the spring of 1971, the unit was heavily engaged on a daily basis 

performing a variety of highly classified cryptologic-related missions. 

On the morning of March 4, 1971, the crew of Vanguard 216 lifted off the runway at 0640 and headed for the 

Demilitarized Zone (DMZ) and southwestern North Vietnam. Overcast skies and wind made for less-than-perfect 

flying conditions, but the temperature was a comfortable 77 degrees. The flight was part of the unit’s effort to 

support “Operation Left Jab,” a mission that used dedicated aircraft to collect a variety of enemy signal and 

voice-related intelligence. On this day their specific purpose was to locate a newly established 

North Vietnamese surface-to-air missile (SAM) site near the DMZ. Confidence was high. “Left 

Jab” had operated for the last three months without incident, and despite the ever present 

danger, the crew anticipated a routine mission. The JU-21D aircraft they flew was basically a 

civilian Beechcraft equipped with the most sophisticated SIGINT collection systems fielded 

by the ASA in Vietnam. The aircraft’s equipment could provide 360-degree direction finding 

coverage, and was the very first to use a digital computer to store data. 
MP 33610

The pilot, Captain Michael Marker, was a native of Wichita Falls, Texas, and received his commission via the 

ROTC program at Midwestern State University. At the time of the flight he was 23 years old and married. 

Serving as his co-pilot was Warrant Officer 1 Harold Algaard. A native of Fosston, Minnesota, by 1971 he was an 

experienced fix-winged pilot with the 138th. He was 22 years old at the time, married, and the father of a sixmonth-old baby.

 In addition to the flight crew, the plane also served as the workplace for three ASA cryptologic professionals: 

Specialist (SP) 6 John Strawn and SP5s Richard Hentz and Rodney Osborn. Strawn was twenty-eight and the 

senior member of the group. He hailed from Salem, Oregon and had been in the military since 1959. By the time 

he deployed to Vietnam in April of 1970, Strawn had become a highly skilled signals intelligence analyst. Hentz 

was from Oshkosh, Wisconsin. An experienced Vietnamese linguist and voice intercept analyst, he had been in 

Vietnam since October of 1970. In March of 1971, he was 23 years old and had a wife and son. Osborne was a 

native of Kent, Washington. Like Strawn, he was an accomplished signal intelligence analyst, and like Hentz had 

been “in country” since the fall of 1970.

Two hours into the flight, all contact with the aircraft was lost. When the plane failed to return at the expected 

time, an intensive search effort was initiated that lasted two days and covered over a 300-mile area. Despite 

these efforts, no trace of the aircraft or the men was found. In addition, the number of hostile forces in the area 

made it impossible to send in ground-based search teams.

 In time, various pieces of intelligence revealed that on March 4, an aerial detonation had occurred in the area 

that matched the altitude and flight pattern of the plane. It was suspected that the aircraft fell prey to the SAM 

site it was attempting to locate. Eventually the status of the crew was changed from missing to “Killed in Action.” 

The aircraft was the last of only three ASA crews lost during the entire Cold War, and it was the only fixed-wing 

ASA plane shot down from the 138th. 

The crew of Vanguard 216 was gone and their fellow soldiers and families mourned their loss, but the memory of 

their service and sacrifice to the cryptologic service and their nation would never be forgotten.

Captain Marker, WO1 Laggard, and Specialist 5 Osborne are all memorialized at the Court of the Missing of the 

National Memorial Cemetery of the Pacific in Hawaii. Specialist 6 Strawn is also memorialized at Cemetery of 

the Pacific as well as at Willamette National Cemetery in Portland, Oregon. Finally, Specialist Hentz’s memorial is 

located at Riverside Cemetery in his home town of Oshkosh, Wisconsin.