Tag Archives: Vietnam War

12 January 1962

ARVN soldiers run to board U.S. Army CH-21C Shawnee helicopters. (LIFE Magazine)
ARVN soldiers run to board U.S. Army CH-21C Shawnee helicopters. (LIFE Magazine)

12 January 1962: The first helicopter assault of th Vietnam War, Operation Chopper, took place when 33 United States Army CH-21C Shawnee transport helicopters of the 8th and 57th Transportation Companies airlifted 1,036 soldiers of the Army of the Republic of Vietnam (ARVN) into battle against an insurgent Việt cộng (National Liberation Front) stronghold, approximately 10 miles (16.1 kilometers) west of Saigon. The landing zone was 150 yards by 300 yards and surrounded by tall trees.

A flight of U.S. Army CH-21C Shawnee helicopters over South Vietnam, 1962. (LIFE Magazine)
A flight of U.S. Army CH-21C Shawnee helicopters over South Vietnam, 1962. (LIFE Magazine)

The Piasecki Helicopter Company CH-21C Shawnee was a single-engine, tandem rotor transport helicopter. It had a flight crew of three with one or two gunners, and could carry up to 20 soldiers under ideal conditions.

With rotors turning, the ship’s overall length was 86 feet, 4 inches (26.314 meters) and it was 15 feet, 9 inches (4.801 meters) high. The rotors were 44 feet (13.411 meters) in diameter and the fuselage was 52 feet, 7 inches (16.027 meters) long. The empty weight was 8,950 pounds (4,059.7 kilograms) and maximum takeoff weight was 15,200 pounds (6,894.6 kilograms).

The forward rotor turned counter-clockwise, as seen from above. (The advancing blade is on the helicopter’s right side.) The rear rotor turns the opposite direction. Normal operating speed for the main rotors was approximately 250 r.p.m. The counter-rotating rotors cancelled out engine torque, eliminating any need for a tail rotor.

The H-21 was powered by a single air-cooled, supercharged, 1,823.129-cubic-inch-displacement (29.875 liter) Wright Aeronautical Division Cyclone 9 863C9WD1 (R-1820-103) nine-cylinder radial, mounted inside the fuselage at midship, and drove the front and rear rotors in opposite directions through drive shafts and gear boxes. The Wright R-1820-103 engine was rated at 1,275 horsepower at 2,500 r.p.m., and 1,425 horsepower at 2,700 r.p.m., for takeoff. This direct-drive engine had a compression ratio of 6.80:1 and required 100/130 aviation gasoline. The engine was 4 feet, 0.50 inches (1.232 meters) long, 4 feet, 6.95 inches (1.396 meters) in diameter, and weighed 1,350 pounds (612 kilograms). Wright built 971 R-1820-103s from November 1950 through 1957.

The CH-21C had a maximum speed of 127 miles per hour (204 kilometers per hour) and a range of 265 miles (427 kilometers). It’s service ceiling was 19,200 feet (5,852.2 meters).

A U.S. Army CH-21C Shawnee over the Landing Zone west of Saigon, 12 January 1962. (U.S. Army)

The Piasecki H-21 Workhorse was developed for the U.S. Air Force as an air base support and search and rescue helicopter in cold weather operations. A total of 707 were built for the U.S., France and Germany, as well as civil operators. 334 were built for the U.S. Army as the H-21C Shawnee, redesignated CH-21C in 1962.

Its performance in the hot and humid climate of Southeast Asia was limited, restricting the troop load to 9 soldiers. It was withdrawn from service in 1964 when the Bell HU-1A Iroquois began to replace it. All CH-21Cs were retired when the CH-47 Chinook assumed its role in 1965.

ARVN troops wait while a U.S. Army CH-21C Shawnee lands. (LIFE Magazine)
ARVN troops wait while a U.S. Army CH-21C Shawnee lands. (LIFE Magazine)

© 2019, Bryan R. Swopes

7 January 1967

John Steinbeck aboard a U.S. Army UH-1 helicopter of D Troop, 1st Squadron, 10th Cavalry Regiment, at Pleiku, Vietnam, 7 January 1967. (Newsday)
John Steinbeck aboard a U.S. Army UH-1B Iroquois helicopter of D Troop, 1st Squadron, 10th Cavalry Regiment, at Pleiku, Vietnam, 7 January 1967. (Newsday)

During 1966–1967, author John Steinbeck was in Vietnam. He wrote a series of dispatches to Newsday which have recently been published as a book, Steinbeck In Vietnam: Dispatches From the War, edited by Thomas E. Barden. University of Virginia Press, 224 pp., $29.95.

On 7 January 1967, Steinbeck was at Pleiku, where he flew aboard a UH-1 Huey helicopter with D Troop, 1st Squadron, 10th Cavalry. He wrote the following about the helicopter pilots:

“I wish I could tell you about these pilots. They make me sick with envy. They ride their vehicles the way a man controls a fine, well-trained quarter horse. They weave along stream beds, rise like swallows to clear trees, they turn and twist and dip like swifts in the evening. I watch their hands and feet on the controls, the delicacy of the coordination reminds me of the sure and seeming slow hands of (Pablo) Casals on the cello. They are truly musicians’ hands and they play their controls like music and they dance them like ballerinas and they make me jealous because I want so much to do it. Remember your child night dream of perfect flight free and wonderful? It’s like that, and sadly I know I never can. My hands are too old and forgetful to take orders from the command center, which speaks of updrafts and side winds, of drift and shift, or ground fire indicated by a tiny puff or flash, or a hit and all these commands must be obeyed by the musicians hands instantly and automatically. I must take my longing out in admiration and the joy of seeing it. Sorry about that leak of ecstasy, Alicia, but I had to get it out or burst.”

Bell UH-1B Iroquois gunship of D Troop, 1st Squadron, 10th Cavalry Regiment, U.S. Army. Vietnam ca. 1966–1967. (U.S. Army)
Bell UH-1B Iroquois gunship of D Troop, 1st Squadron, 10th Cavalry Regiment, U.S. Army. Vietnam, ca. 1966–1967. (U.S. Army)
Author John Steinbeck observes the Vietnam War from a U.S. Army UH-1B "Huey" helicopter. A gunner mans an M60 7.62mm machine gun. (Associated Press)
Author John Steinbeck observes the Vietnam War from a U.S. Army UH-1B “Huey” helicopter. A gunner mans an M60 7.62mm machine gun. (Associated Press)

© 2014, Bryan R. Swopes

Medal of Honor, Major Patrick Henry Brady, Medical Service Corps, United States Army.

Major Patrick Henry Brady, Medical Service Corps, United States Army. (AMEDD)

The President of the United States in the name of The Congress takes pleasure in presenting the MEDAL OF HONOR to


Medical Service Corps, United States Army

for service as set forth in the following


Major Patrick Henry Brady, Medical Corps, United States Army
Major Patrick Henry Brady, Medical Service Corps, United States Army

For conspicuous gallantry and intrepidity in action at the risk of his life above and beyond the call of duty, Maj. Brady distinguished himself while serving in the Republic of Vietnam commanding a UH-1H ambulance helicopter, volunteered to rescue wounded men from a site in enemy held territory which was reported to be heavily defended and to be blanketed by fog. To reach the site he descended through heavy fog and smoke and hovered slowly along a valley trail, turning his ship sideward to blow away the fog with the backwash from his rotor blades. Despite the unchallenged, close-range enemy fire, he found the dangerously small site, where he successfully landed and evacuated 2 badly wounded South Vietnamese soldiers. He was then called to another area completely covered by dense fog where American casualties lay only 50 meters from the enemy. Two aircraft had previously been shot down and others had made unsuccessful attempts to reach this site earlier in the day. With unmatched skill and extraordinary courage, Maj. Brady made 4 flights to this embattled landing zone and successfully rescued all the wounded. On his third mission of the day Maj. Brady once again landed at a site surrounded by the enemy. The friendly ground force, pinned down by enemy fire, had been unable to reach and secure the landing zone. Although his aircraft had been badly damaged and his controls partially shot away during his initial entry into this area, he returned minutes later and rescued the remaining injured. Shortly thereafter, obtaining a replacement aircraft, Maj. Brady was requested to land in an enemy minefield where a platoon of American soldiers was trapped. A mine detonated near his helicopter, wounding 2 crewmembers and damaging his ship. In spite of this, he managed to fly 6 severely injured patients to medical aid. Throughout that day Maj. Brady utilized 3 helicopters to evacuate a total of 51 seriously wounded men, many of whom would have perished without prompt medical treatment. Maj. Brady’s bravery was in the highest traditions of the military service and reflects great credit upon himself and the U.S. Army.

// Richard M. Nixon//


Call sign, "Dust Off." (U.S. Army)
Call sign, “Dust Off.” (U.S. Army)

Major General Patrick Henry Brady was born 1 October 1936 at Philip, South Dakota, the son of Michael and LaVona Brady. He attended O’Dea High School, Seattle, Washington, and then graduated from Seattle University with a bachelor’s degree in psychology. As a member of the Reserve Officers Training Corps (ROTC), he received a commission as a second lieutenant in the Medical Service Corps, United States Army Reserve, 20 March 1959.

On 17 September 1959, 2nd Lieutenant Brady was transferred to the Regular Army, with his date of rank retroactive to 8 April 1959. He was promoted to 1st lieutenant, 8 April 1962. Lieutenant Brady served in Berlin, Germany from 1959 to 1963. Lieutenant Brady was promoted to the rank of captain, Army of the United States (AUS), 8 April 1963. (Brady’s permanent rank in the Regular Army was advanced to captain, 8 April 1966.)

In 1963, Brady was sent to the Army Aviation School at Fort Rucker, Alabama, to be trained as a helicopter pilot. He received his wings in December and the following month was sent to the Republic of Vietnam, assigned to the 57th Medical Detachment (Helicopter Ambulance).

When the unit’s commanding officer was killed in action, Captain Brady assumed command of the 57th’s Detachment A at Sóc Trăng Airfield. After completing his combat tour, Captain Brady was assigned as a helicopter pilot at Fort Benning, Georgia.

Major Patrick Henry Brady in the cockpit of a UH-1 Huey “Dust Off” medical evacuation helicopter, Republic of Vietnam, circa 1968. (VHPA)

Captain Brady was promoted to the rank of major, 3 July 1967. In 1967 he was reassigned to the 54th Medical Detachment (Helicopter Ambulance), 67th Medical Group, 44th Medical Brigade, and after the unit completed training, deployed to Chu Lai, Vietnam. It was while serving with this unit that he flew the missions for which he was awarded the Medal of Honor.

The Medal of Honor was presented to Major Brady by President Richard M. Nixon in a ceremony at The White House, Washington, D.C., 9 October 1969.

President Richard M. Nixon presented the Medal of Honor to four soldiers of the United States Army at The White House, 9 October 1969. Left to right: Sergeant Robert Martin Patterson, Captain James Michael Sprayberry, President Nixon, Captain Jack Howard Jacobs, and Major Patrick Henry Brady. (NBC News)

During two combat tours in Vietnam, Major Brady flew more than 2,000 combat missions and rescued as many as 5,000 wounded soldiers.

Patrick Brady served in the United States Army for thirty-four years, rising to the rank of Major General. Major General Brady has been awarded the Medal of Honor, Distinguished Service Cross, Distinguished Service Medal with oak leaf cluster (two awards), Defense Superior Service Medal, Legion of Merit, Distinguished Flying Cross with silver oak leaf cluster (six awards), Bronze Star with one oak leaf cluster (two awards) with “V” Device (“participation in acts of heroism involving conflict with an armed enemy”), Purple Heart, Meritorious Service Medal with two oak leaf clusters (three awards), Air Medal with “V” Device (52 awards), and Army Commendation Medal with oak leaf cluster (two awards).

Major General Patrick Henry Brady, Medical Corps, United States Army

Major General Brady retired in 1983 and lives in Sumner, just south of Auburn, Washington, with his wife, the former Nancy Lee Parsek, whom he met in high school. They have six children. Two are graduates of the United States Military Academy at West Point, New York. A daughter, Meghan Brady, who also graduated from the ROTC unit at Seattle University, served as an officer in the Medical Service Corps with duty in Kosovo and the invasion of Iraq. Captain Brady was awarded the Bronze Star.

Major General Brady and Captain Brady are co-authors of Dead Men Flying: Victory in Vietnam (WND Books, 2012).

Major General Patrick Henry Brady, U.S. Army (retired) with Senator John Cornyn of Texas, as they announce The Dust Off Crews of the Vietnam War Congressional Gold Medal Act, at Fort Sam Houston, Texas, 11 November 2015. (U.S Army)
Major General Patrick Henry Brady, U.S. Army (retired) with Senator John Cornyn of Texas, as they announce The Dust Off Crews of the Vietnam War Congressional Gold Medal Act, at Fort Sam Houston, Texas, 11 November 2015. (U.S Army)

The Bell Helicopter Co. UH-1H Iroquois (Model 205A-1) is an improved variant of the UH-1D (Model 205), which was itself derived from the UH-1B (Model 204). The type’s initial military designation was HU-1, and this resulted in the helicopter being universally known as the “Huey.”

The UH-1H is a single main rotor/tail rotor medium helicopter powered by a turboshaft engine. It can be flown by a single pilot, but is commonly flown by two pilots in military service. The helicopter has an overall length of 57 feet, 0.67 inches (17.375 meters) with rotors turning. The fuselage is 41 feet, 5 inches (12.624 meters) long. The two blade semi-rigid, under-slung main rotor has a diameter of 48 feet, 3.2 inches (14.712 meters), and turns counter clockwise when viewed from above. (The advancing blade is on the helicopter’s right.) At 100% NR, the main rotor turns 324 r.p.m. The two blade tail rotor assembly has a diameter of 8 feet, 6 inches (2.591 meters). It is on the left side of the pylon in a pusher configuration and turns counter-clockwise as seen from the helicopter’s left. (The advancing blade is above the axis of rotation.) The helicopter has a height of 13 feet, 7.4 inches (4.150 meters), measured to the top of the mast.

A Bell UH-1H helicopter ambulance, Vietnam, 1969.
A Bell UH-1H helicopter ambulance, Vietnam, 1968. (John Metcalf, “Dustoff 68,” via dustoff.net)

The UH-1H is powered by a Lycoming LTC1K-4 (T53-L-13) turboshaft engine rated at 1,400 shaft horsepower, though it is derated to the helicopter’s transmission limit. The T53-L-13 is a two-shaft free turbine with a 6-stage compressor (5 axial-flow stages, 1 centrifugal-flow stage) and a 4-stage axial-flow turbine (2 high-pressure stages, 2 low-pressure power turbine stages). The T53-L-13 is 3 feet, 11.9 inches (1.217 meters) long, 1 foot, 11.0 inches (0.584 meters) in diameter and weighs 549 pounds (249 kilograms).

The UH-1H has a maximum gross weight of 9,500 pounds (4,309.1 kilograms). Its maximum speed, VNE, is 124 knots (143 miles per hour, 230 kilometers per hour). With full fuel, 206.5 gallons (781.7 liters), the helicopter has a maximum endurance of three hours.

5,345 UH-1H Hueys were built, and many of the earlier UH-1Ds were upgraded to the UH-1H standard.

A Bell UH-1H medevac helicopter returns to its base, while ground personnel standby to offload the injured. (U.S. Army)
A Bell UH-1H medevac helicopter landing while ground personnel standby to offload the injured. (Free Republic)

© 2019, Bryan R. Swopes

2 January 1967

“MiG Sweep,” by Keith Ferris. Colonel Robin Olds uses a Vector Roll to gain firing position on a MiG-21 fighter. “I got on top of him and half upside down, hung there, and waited for him to complete more of his turn. . . .”

2 January 1967: This painting, MiG Sweep, by aviation artist Keith Ferris, depicts “Olds 01” during OPERATION BOLO. The twin-engine all-weather jet fighter, a McDonnell F-4C -21-MC Phantom II, serial number 63-7680, was flown by Colonel Robin Olds, USAF, with First Lieutenant Charles C. Clifton, USAF, as the Weapons System Operator.

The Phantom is  shown inverted as Colonel Olds maneuvers to fire an AIM-9B Sidewinder heat-seeking missile at a North Vietnamese Mikoyan-Gurevich MiG-21 over Hanoi. Robin Olds was the only U.S. Air Force ace with victories in both World War II and Vietnam.

Colonel Robin Olds, United States Air Force
Colonel Robin Olds, United States Air Force, Wing Commander, 8th Tactical Fighter Wing. (U.S. Air Force)

The area around Hanoi, North Vietnam, was the most heavily defended target area ever encountered by the United States Air Force. A combination of radar-directed anti-aircraft artillery, surface-to-air guided missiles, and fighter interceptors made every mission very dangerous. Republic F-105 Thunderchief fighter bombers were taking heavy losses to the Soviet-built Mikoyan-Gurevich MiG-21PFL fighters. When escorting F-4C Phantoms would try to engage the MiGs, they would return to their bases which were safe from attack under the American rules of engagement.

Colonel Robin Olds with Captain John (“J.B.”) Stone, 433rd Tactical Fighter Squadron, one of the planners of OPERATION BOLO. (U. S. Air Force)

OPERATION BOLO was a complex plan to lure the ground-controlled MiG 21s into an air battle by having the Phantoms simulate a Thunderchief attack. Colonel Olds led 48 McDonnell F-4Cs of the 8th and 366th Tactical Fighter Wings on the same type of attack that would have been used by the Thunderchiefs, but rather than carrying a full load of bombs, the F-4s were armed with AIM-7E Sparrow radar-guided missiles and AIM-9B Sidewinder heat-seeking missiles. (The F-4C was not armed with a gun.)

A Mikoyan Gurevich MiG-21PF at the National Museum of the United States Air Force.
An Aero Vodochody-built Mikoyan-Gurevich MiG-21F-13 with the markings of the Vietnam Peoples’ Air Force at the National Museum of the United States Air Force, Wright-Patterson Air Force Base, Ohio. (U.S. Air Force)

As the Mach 2+ MiG 21s started coming up through the clouds, their pilots quickly realized that instead of the vulnerable targets of F-105s on a bomb run, they were faced with air superiority fighters.

In the official after action report, Colonel Olds said,

#000000; font-family: courier new, courier;">At the onset of this battle, the MiGs popped up out of the clouds. Unfortunately, the first one to pop through came up at my 6 o’clock position. I think this was more by chance than by design. As it turned out, within the next few moments, many others popped out of the clouds in varying positions around the clock.

#000000; font-family: courier new, courier;">This one was just lucky. He was called out by the second flight that had entered the area, they were looking down on my flight and saw the MiG-21 appear. I broke left, turning just hard enough to throw off his deflection, waiting for my three and four men to slice in on him. At the same time I saw another MiG pop out of the clouds in a wide turn about my 11 o’clock position, a mile and a half away. I went after him and ignored the one behind me. I fired missiles at him just as he disappeared into the clouds.

#000000; font-family: courier new, courier;">I’d seen another pop out in my 10 o’clock position, going from my right to left; in other words, just about across the circle from me. When the first MiG I fired at disappeared, I slammed full afterburner and pulled in hard to gain position on this second MiG. I pulled the nose up high about 45 degrees, inside his circle. Mind you, he was turning around to the left so I pulled the nose up high and rolled to the right. This is known as a vector roll. I got on top of him and half upside down, hung there, and waited for him to complete more of his turn and I timed it so that as I continued to roll down behind him, I’d be about 20 degrees angle off and about 4,500 to 5,000 feet behind him. That’s exactly what happened. Frankly, I’m not sure he ever saw me. When I got down low and behind, and he was outlined by the sun against a brilliant blue sky, I let him have two Sidewinders, one of which hit and blew his right wing off.

Aces and Aerial Victories: The United States Air Force in Southeast Asia 1965–1973, by R. Frank Futrell, William H. Greenhalgh, Carl Grubb, Gerard E. Hasselwander, Robert F. Jakob and Charles A. Ravenstein, Office of Air Force History, Headquarters USAF, 1976, Chapter II at Page 39.

The F-4Cs succeeded in shooting down seven MiG 21s, with another two probably destroyed. This accounted for about half of the VPAF’s MiG 21 complement.

With another flight crew, the Phantom flown by Robin Olds on 2 January 1967, McDonnell F-4C-21-MC 63-7680, shot down a MiG 17 on 13 May 1967. It was itself shot down by antiaircraft fire while attacking a SAM site, 20 November 1967. The Weapons System Officer, 1st Lieutenant James L. Badley, bailed out and was rescued, but the pilot, Captain John M. Martin, was not seen to leave the aircraft and is listed as Missing in Action.

Colonel Robin Olds shot down two MiG-17 fighters with this McDonnell F-4C-21-MC Phantom II, 63-7680. (U.S. Air Force)
Colonel Robin Olds shot down a MiG 21 interceptor with this McDonnell F-4C-21-MC Phantom II, 63-7680, photographed at Ubon RTAFB, sometime between March and November 1967. (Photograph by Frank R. MacSorley, Jr.)

© 2019, Bryan R. Swopes

20 December 1969

Senior Lieutenant Nguyễn Văn Cốc in the cockpit of a MiG 21. (From the collection of CMSGT Bob Laymon, USAF)

20 December 1969: Senior Lieutenant Nguyễn Văn Cốc, of the 921st Fighter Regiment, Vietnam Peoples’ Air Force, flying a Mikoyan-Gurevich Mig 21PFL supersonic interceptor, shot down his final enemy aircraft of the Vietnam War, a U.S. Air Force AQM-34L  reconnaissance drone (Ryan Aeronautical Company Model 147SC, code named BUFFALO HUNTER).

A U.S. Air Force Ryan AQM-34L Buffalo Hunter of the 556th Reconnaissance Squadron, based at Bien Hoa Air Base, circa 1969. This drone flew 68 missions before being shot down over Hanoi. (U.S. Air Force)

Nguyễn Văn Cốc entered the Không quân Nhân dân Việt Nam (Vietnamese People’s Air Force) in 1961. He spent four years in the Soviet Union training as a fighter pilot, and was qualified on both the Mikoyan-Gurevich MiG 17 and MiG 21.

Nguyễn was credited by the VPAF with nine aerial combat victories. Seven of these were also confirmed by the United States. Between 30 April 1967 and 20 December 1969, he shot down a Convair F-102A Delta Dart, three Republic F-105D Thunderchiefs, one F-105F Thunderchief, a McDonnell F-4B Phantom II, two F-4D Phantom IIs, and the BUFFALO HUNTER.

Senior Lieutenant Nguyễn Văn Cốc, at right, with two other pilots. A Mikoyan-Gurevich MiG 21PF is in the background. (VPAF)

All of Nguyễn’s victories were scored while flying the MiG 21PFL, with R-3S infrared-homing air-to-air missiles.

These MiG 21s are assigned to the 921st Fighter Regiment. The closest, “Red 4326,” is one of the interceptors flown by Nguyễn Văn Cốc. The 13 “kill marks” on its nose represent enemy aircraft shot down by Nguyễn and other pilots who flew the airplane. This airplane is on display at the Hanoi Air Defense Museum (Bảo tàng Phòng không-Không quân). (VPAF)

The R-3S (also known as the K-13, and identified as “AA-2A Atoll” by NATO forces) was reverse-engineered by the Turopov Design Bureau, Tushino, Russia, from a Raytheon AIM-9B Sidewinder which had been captured by the People’s Republic of China during the 1958 Taiwan Straits Crisis. Fired by a Republic of China Air Force F-86 Sabre, the missile hit a People’s Liberation Army Air Force MiG 17, but its warhead did not detonate. The PLAAF turned the Sidewinder over to the Soviet Union.

Lieutenant General Nguyễn remained in the VPAF until retiring in 2002 with the rank of chief inspector. He is the highest-scoring fighter pilot of the Vietnam War.

Captain Nguyễn Văn Cốc is congratulated by Hồ Chí Minh, President of the Democratic Republic of Vietnam.

The BUFFALO HUNTER was approximately 26 feet (7.9 meters) long with a wing span of 13 feet (4.0 meters). It weighed 3,067 pounds (1,391 kilograms).

The drone was powered by a single Continental J69 turbojet engine, rated at 1,920 pounds of thrust (8.54 kilonewtons).

BUFFLO HUNTERS had a  cruising speed of 500–540 knots (575–621 miles per hour/926-1,000 kilometers per hour), but could reach 590 knots (679 miles per hour/1,093 kilometers per hour) “on the deck.” It had a maximum range of 650 nautical miles (748 statute miles/1,204 kilometers).

The drone was equipped with a Fairchild 415Y reconnaissance camera. It carried 1,800 feet (549 meters) of 70-millimeter film.

BUFFALO HUNTERs were launched by Lockheed DC-130 drone carriers, modified from C130 A or -E Hercules transports. Most carried two drones on underwing pylons, but two of the DC-130s could carry four.

A Lockheed DC-130 carrying two BUFFALO HUNTER reconnaissance drones. (U.S. Air Force)

© 2018, Bryan R. Swopes