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Interdiction on the Ho Chi Minh Trail

Air Force Magazine Online
October 1971 (Reprint)

 NIMROD - King of the Trail
By Capt. Michael J. C. Roth, USAF
In 1966, the first A-26s – Call sign “Nimrod” --- began operating out of Thailand’s Nakhon Phanom Air Base against the Ho Chi Minh Trail. A former A-26 pilot of the 609th Air Commando Squadron tells of his experiences in this sturdy Douglas light bomber, a machine that first saw combat in World War II, was dusted off for Korea, and now has served with distinction in Southeast Asia --- a truly remarkable retread …

The author, Capt. Michael J. C. Roth, is a 1963 graduate of the Air Force Academy. Following pilot training, he served for three years as a SAC KC- 135 crew member. In 1967 and 1968, Captain Roth flew A-26s in Southeast Asia. After two years as a graduate student in management at the University of Southern California, he was stationed in Japan as a WC-135 pilot and as transportation officer at Yakota AB. He has recently been assigned to the Systems Program Management office at Wright-Patterson AFB, OH

One day in the spring of 1964 we had an unscheduled arrival at Williams AFB, Ariz. I was then about halfway through basic pilot training in the T-38, and this stranger on the ramp aroused my curiosity. It was a Douglas B-26 – the World War II “Invader, “Known until 1948 as the A-26 – on its way to the boneyard at Davis Monthan AFB. The poor old girl couldn’t quite make it all the way to her final resting place.

At the time, I was occupied with things like afterburners and flight director systems. I looked on this surprise visit as one, perhaps only, chance to get a close-up look at a disappearing species. It would have surprised me to learn that, as I looked over this old prop-driven airplane, forty other B-26s were being completely rebuilt by the On Mark Engineering Co. of Van Nuys, Calif. And it would have been an even bigger surprise to know that four years later, I would be returning from Thailand, utterly convinced that this aircraft, which I had by then flown in combat, was a magnificent machine.

As I looked over the B-26 at Williams that day, I recalled some of the things I’d heard about it. There was the story of a B-26 in Korea pulling up on the wing of a Mustang, feathering an engine, and staying right in formation with the F-51, though the fighter pilot had his throttle firewalled.

And there was one about the B-26 pilot who had run a North Korean truck over a cliff at night by coming in on the deck with his landing lights shining into the truck driver’s eyes. Were the stories true? I couldn’t say for sure. But they did give the airplane a certain aura. By 1964, however, that aura was tarnished by stories of B-26s losing wings in flight, and there was little doubt in my mind that the airplane was finished.

A Shock to a Jet Pilot

Then in June 1967, I stood on the ramp at England AFB, LA, and looked at the airplane I had just been assigned to fly: the On Mark-modified B-26K, which had been redesignated the A- 26. I quickly found out that this was not the speedster from Korea. Though it was claimed to have a top speed of 305 knots with external armaments (which in itself was somewhat less than a firewalled Mustang), the airplane actually cruised at a little over half that speed. The reason was some of the modification done on the old B-26: a beefed-up wing, permanent wingtip tanks, greater internal fuel capacity, and increased armament capability.

The inner workings of this airplane were a real shock to a young captain who had nothing but jet experience. The main compass was similar to that used as a second backup on the KC- 135 I had been flying. The instruments in front of the right seat were vacuum driven, something that had been mentioned back at Williams only as an interesting historical note. The oxygen regulator was the oldest type I had ever seen, but I was reassured on that point. The oxygen system purged and never used. And there was one distinctly disturbing thing about the airplane --- no ejection seats. To bail out, you simply jettisoned the canopies and dived over the wing.

Perhaps most bewildering of all to a jet pilot, used to only throttles, was the array of levers to control props, mixtures, and carburetor heat. I remember so well some of the early questions like, “What’s a jug?” and, “If I want to go fast, what do I push?”

The program at England AFB answered those, but raised one other big question that took a long time to answer. The airplane was slow, but stable. It maneuvered decently if you supplied the muscle. If you exerted all of your strength and got an assist from the navigator, you might even be able to pull the maximum allowable Gs. So the big question became, “Why this airplane at this time?”

To SEA in the A-26

In eight weeks at England AFB I learned to land the A-26 decently and to deliver ordnance with it passably. I was then sent to the 609th Air Commando Squadron at Nakhon Phanom Royal Thai Air Force Base, familiarly know as NKP. This organization had brought the first A-26s to Southeast Asia in 1966, and began using them in one of the most demanding missions in the history of aerial warfare --- interdicting the Ho Chi Minh Trail. The 609th adopted the permanent call sign “Nimrod.”

The Nimrod mission was unusually demanding because of the combination of obstacles it had to overcome. The Ho Chi Minh Trail itself was --- and is --- a vast network of vehicular roads, footpaths, and staging areas. It comes out of North Vietnam in a number of places from Mu Gia Pass down to the DMZ, winds through Laos, and enters South Vietnam in the vicinity of Khe Sanh and several more southerly points.

The terrain through which it runs is spectacular. Rugged, 5000-foot mountains are interspersed with wide river valleys. From the floors of those valleys jagged limestone formations, called karst, rise hundreds of feet straight up. And covering it all is a dense rain forest that in some places is triple tiered. The main roads, with a few exceptions, are visible from the air, but the footpaths and way stations are hidden under the forest canopy.

This road network was protected by an array of antiaircraft guns that ranged from 12.7 mm up to 57 mm. Here was a partial answer to my big question. For some reason, up until I left the Nimrods in 1968, the Communists never brought SAMs or radar-controlled guns into the area. Since the vast majority of traffic moved at night, all A-26 missions were flown in the dark. This gave us a sporting chance to survive in a gun environment that would have been disastrous in daylight. But the darkness was a two-edged sword. It greatly complicated our search for targets.

In September 1967, when I arrived at NKP, there were no operational strike aircraft equipped with night target-detection devices such as those on the AC-130 and AC-119 gunships now flying the Trail. The problem of pinpointing and hitting targets on the Trail at night was solved by teamwork between the FACs in O-2s, C-123s and C-130s, and the strike aircraft.

The equipment used by the FACs enabled them to visually spot truck on the roads, even on the darkest nights. Truck sightings by our FACs numbered well into the thousands each month during the dry season, from October through April, and included some vehicles as large as moving vans.

Teamwork on the Trail

When the FACs picked up a target, they had to reference its position on the ground to something that could be seen and identified in the dark by a strike pilot’s unaided eye. Flares were used frequently to illuminate targets, but most pilots preferred the protection afforded by the darkness. The reference was usually a fire --- perhaps one left from a previous strike or from a marker dropped by the FAC. This required precise communication, and FACs frequently met with strike crews to work out exact descriptive wording.

Once the strike pilot was satisfied that he had sighted the reference that the FAC was describing and could locate the target, he would launch a strike. After the first strike, the FAC could guide the strike pilot further by making corrections from the point of the initial strike.

And here was the rest of the answer to my big question: “Why the A-26?” Under prevailing conditions, the A-26 could run through this process with better results than any other airplane the Air Force could put into the air.

The reasons are not mysterious. The airplane was equipped with eight external ordnance pylons, a large bomb bay, and eight .50 caliber machine guns in the nose. It could carry a maximum armament load of 11,000 pounds and had a combat radius of 575miles, which allowed an hour and a half over the target and a half hour of reserve fuel. Since most of the Ho Chi Minh Trail is within 200 miles of NKP, the time on target could be considerably over an hour and a half.

Because of the airplane’s low speed and adequate maneuverability, the Nimrod pilot could cruise at a low enough altitude to easily pick out reference points the FACs were using, go from there to his target, and roll into his attack pattern from that same low altitude.

The A-26 was also an extremely stable platform, which made for very good bombing and strafing accuracy. And, finally, the airplane was rugged. I know of A-26s that took hits in the props and engines and still managed to land with both engines running.

A Big Night for Nimrod

Of the 146 missions I flew, I think perhaps the one that best demonstrated the great value of the airplane took place on April 5, 1968. On that night I was assigned to work with an O-2 FAC on a short stretch of the Trail about sixty miles due east of NKP.

As often happened, we searched for a long time without sighting a single truck on the road. The movement of trucks usually took place in short spurts of activity, and trucks seldom, if ever, made the entire trip from North to South Vietnam in one night.

A little over an hour after arriving on station, my FAC sighted two trucks on the road. He dropped a flare and marked them with a rocket.. I made two passes with hard bombs. The FAC then confirmed that I had destroyed one of the trucks, but, before he could determine the exact whereabouts of the other, he began to have airplane problems, and had to return home. A radio check with other FACs at different locations on the Trail revealed that there was no other activity. So I began an unaided visual search of my assigned road section.

At this point, I should say that a more proper pronoun to use in referring to the A-26 is “we.” Each airplane carried a pilot in the left seat and a navigator in the right. My navigator, Lt. Col. Francis L. McMullen, is one o the finest men it has been my privilege to know in the Air Force. His navigation duties were minimal, since he had no tools other than a map.

TACAN was the primary method of navigating, and the pilot was able to operate that alone. The navigator’s main job, according to the checklist, was to operate the armament and fuel systems. In the course of their tours, however, our navigators actually became second pilots. Every one of them, I believe, was capable of flying the airplane home and landing it. Two A-26 navigators that I knew are now pilots --- one in F-4s and the other in B-57s.


After our FAC returned to NKP that night, we spent another half hour searching over our assigned area before sighting something. That “something” was a 37-mm anti-aircraft gun that fired tow clips at us.

I was able to pinpoint his position in the dark because of three small fires on the ground that surrounded him, probably unknown to the gun crew. We flew high over the gun’s position to get a TACAN reading and then checked it on our map. It was well off any road, and in an area where there were no known villages.

Colonel McMullen gave me the elevation of the terrain at the gun position and figured out the best heading for a pass on it. Through we carried flares, we knew it was to our advantage to attack a gun in the dark. We rolled in and laid CBUs (cluster bomb units) across the triangle formed by our three reference fires.

One of the bomblets scored a direct hit on some munitions that flared into an intense pinpoint of white fire, sending rays of light through the trees almost like a spot-light. Colonel McMullen saw three more guns come up during our first pass, but we chose to ignore them and concentrate on the fire we had started.

After climbing back up to our base altitude, we informed the nearest FAC, a C-123, that we had a good target for him to look over, He started for our position, bringing with him the A-26 with which he was working. Since we had already been out for more than three hours and fuel was beginning to become a problem, we decided to lay more ordnance around our first strike rather than wait for the C-123.

Three more passes on the target with fire bombs turned the area into an inferno. We could see secondary explosions every few seconds, and our incoming friends had no trouble finding their new target. We remained in the area while the C-123 made a pass over the growing fire.

His observer shouted over the radio, “My God, you found a truck park!” He counted eight burning trucks and said that the secondary explosions were coming from oil drums and crated cargo laid out on the ground. As we departed for NKP we heard him begin to brief his A-26 on the target.

This was a particularly good mission because of the target we had found --- the truck park. The objective of interdiction is, of course, to stop the enemy’s supplies from reaching him. We learned that destroying trucks on the Trail and putting craters in the roads made the enemy’s logistics operation more difficult, but was not coming close to achieving the objective. Obviously the Communists were getting enough supplies down the Trail to support a very large war in South Vietnam.

Bombing the road system itself was an almost futile exercise, because of the many bypasses and alternates available and because of the large labor force permanently stationed on the Trail. Thus, it was especially satisfying to find and hit one of the large caches of supplies destined for South Vietnam. We found them occasionally, but not often enough.

Magnificent Airplane

The A-26 was a magnificent airplane. It did its job better than any other could have, and I’m sure that any pilot could share my attachment to the Nimrod. But, I also have tremendous admiration for the other aircrews and airplanes that worked the Trail. The FACS, whether in O-2s, C-123s, or C-130s, were the indispensable eyes of the team. Un-armed or lightly armed, they braved all the gunfire that came up at us. I never saw a FAC get chased off a target by ground fire.

The other members of the strike force are equally deserving of praise. During the early part of my tour, we frequently worked with T-28s, whose call sign was “Zorro.” I was told at one of my early briefings at NKP that “if a Zorro can find a truck, he’ll get it every time.” I soon learned that this was true. The Zorro pilots finally wore out their T-28s, and near the end of my tour reappeared on the Trail in A-1s, as deadly as before.

Another group of pilots I really respected were our friends in the B-57s, out of South Vietnam. The B-57 came closest to matching the capabilities of the A-26 for this mission, and it was always a pleasure to team up with one. The B-57 crews I saw were all gutty, excellent marksmen.

The F-4s that worked the Trail with us were obviously a different class of airplane from those I’ve mentioned. Their greater speed, wider patterns, and higher roll-in altitudes were all drawbacks for night strikes. Even so, I saw many F-4 pilots lay their ordnance exactly where the FACs wanted it.

But for me, the Nimrod will always be King of the Trail. I feel fortunate to have had an opportunity to fly it. It made me a part of something I thought I could only look at --- like a museum piece --- as I did that day in 1964 at Williams AFB. Nimrod was a mighty hunter and its crews, proud men.