The Iron Butterfly: Brown Water Warriors of Viet-Nam

River Division 593 was born on 1 May 1968, when Lt. William Straight and his men, then at Nha Be, RVN, received a message from Commander Naval Forces Viet-Nam activating River Section 544. Although Lt. Straight had no boats at the time, he started the process of setting up a new unit. On 4 May 68 the first three new MK-11 river patrol boats (PBRs) hull numbers 752, 753 and 754 arrived and Lt. Straight’s men took possession. Test firing the weapons began the same day, and boat trials started the next morning. On 17 May the final seven boats, hull numbers 755, 756, 761, 840, 841, 842 and 843 were received — 544 was now a complete section.

After only three months of operations as River Section 544, during which hundreds of hours had been logged on patrol, a major restructuring within Naval Forces Viet-Nam came about. On 1 Sep 68, with a new organization in place, River Division 593 emerged from an already legendary start and continued in the traditions of the great American “Brown Water Navy.”

Killer jungle

In the first months of operations, 593 was based at Nha Be U.S. Naval Base, and was assigned the task of patrolling the rivers and waterways of the Rung Sat Special Zone. “Rung Sat” in Vietnamese means “Killer Jungle” and had been a very bad area even before the United States became involved in Viet-Nam. The Rung Sat was of special importance to U.S. forces and their war effort because the main shipping channels from the South China Sea to the capitol of Saigon lay mainly in the Rung Sat. Its rivers and jungles were infested with Viet Cong guerrillas and North Vietnamese Army Regulars.

The Rung Sat was approximately 400 square miles and, in the monsoon season, 85% of it was under water. The eastern boundary was along the Thi Vi River (Song Thi Vi). It was known as the Thi Vi-Go Gia area because of the rivers and was very lush and green and provided many areas for the enemy to hide. The headquarters for all of the Rung Sat was in this area, but it was never found. The division spent many hours patrolling the area and it seemed that every day a patrol would be involved in a firefight that resulted in injury, death or, at least, damage to a boat. The western boundary of the Rung Sat was the Soi Rap River (Song Soi Rap). This river was largely defoliated on the eastern bank but, because the western bank was out of the Rung Sat, it was left alone. This side was a jungle maze of thick tropical growth that offered great cover for the enemy and served as a major staging area for attacks on Saigon.
This was the first area that we patrolled in the zone, and was where the legend began.

The division was moved from one side of the zone to the other and then to the Long Tau River (Song Long Tau); this was the major shipping channel from the South China Sea to Saigon and 60% of all the supplies for the war effort came up this river. The Long Tau flowed through the middle of the zone and was very narrow in several spots. If the enemy could have sunk a ship in any one of these areas it would have blocked the main shipping channel for a very long time. The division was on constant patrol on this river, and not one ship was ever lost to enemy rockets while the “Iron Butterfly” was present.

The division took its assigned task to heart and began cleaning up the area with a vengeance. Although several of the men were wounded in action during this time, it was not until 8 Nov 68 that the division had its first member KIA. During a firefight that afternoon, Chief Quartermaster Ted Smith was killed instantly when he was hit by an enemy rocket while aiding one of his men who had been wounded earlier. The death of Chief Smith had a sobering effect on the rest of the men, and everyone was more determined than ever to do the job.

In Viet-Nam, when one area became more important, units would be moved in to patrol it. This also came about when the enemy moved his main base of operations from one area to another; units were then required to move into the new area and patrol it. River Division 593 was one of the first divisions on the Vam Co Dong River (Song Vam Co Dong) when Operation Giant Slingshot began its stranglehold on Viet-Cong Communist aggressors and North Vietnamese Army supply routes from Cambodia to Saigon.

Giant Slingshot

The Giant Slingshot area was a wedge-shaped piece of land bounded by the Vam Co Dong on the north and the Vam Co Tay River (Song Vam Co Tay) on the south. The handle of the slingshot was formed by the Vam Co River (Song Vam Co), which was partially in our old operation area, the Rung Sat. The slingshot area was just north of the Mekong Delta and just below the famous Plain of Reeds; Cambodia was to the west. It was an easy two-day march from Cambodia to Saigon with a supply/rest stop in the wedge. This was why we were sent in; they wanted this pattern disrupted and the enemy to be denied this area for his operations.

The USS Harnett Country (LST 821) was moved up river from the South China Sea to the bridge at Ben Luc and was utilized as an operating base for 593 and a detachment of Seawolf helicopters. Ben Luc was a commercial center at the junction of the Vam Co Dong River and Highway 4, the main overland link between Saigon and the Delta area. The division remained on this operation from 12 Dec 68 to 25 Mar 69. During this time, Lt. Bill Straight was relieved by Lt. L.A. Bissonnette, and the division lost PBR 753 when it was hit by two enemy rockets during a firefight on 16 Feb. The boat burned out of control and, even with a gallant effort by its crew, it could not be saved and finally blew up. Luckily no one was killed in this action, but the division had already had one man killed on Slingshot. On 17 Jan. Engineerman Second Class Terry Simison was shot in the head by an enemy AK-47 round during a firefight and died on the medevac en route to the field hospital. So, when no one was killed on 753, everyone in the division felt relieved. This feeling would be short-lived because, on 17 Feb, the day after losing 753, Petty Officer C.A. McCafferty was hit by an enemy rocket during a heated firefight and was killed instantly.

The rivers and canals in the Slingshot operation area were narrow, to say the least. The banks were covered with thick, lush jungle and many bunker complexes were hid in the high banks and tree lines that bordered the river. The enemy had a stronghold there and did not want to give it up. Firefights were often, and brutal, and came with no warning. Charlie soon realized that the “Iron Butterfly” was as determined as he was, and that the ratio of dead he was giving up was too high a price to pay. Soon, the majority of enemy units bypassed the area, and firefights were less frequent. Over 50% casualties were suffered by the men of River Division 593 during its stay on operation Giant Slingshot so everyone was happy when word came down that the division was moving back to Nha Be on 25 Mar 69 and would, once again, be patrolling the Rung Sat Special Zone.

The idea of being back in the Rung Sat had not yet settled in when the Division had another member KIA. GMG3 Thomas L. Brown, forward gunner on PBR 756, was killed on the night of 9 Apr when an enemy B40 rocket flew out of the dark during a firefight and cut his gun tub in half. Petty Officer Brown was killed instantly.

During the months that followed, the Rung Sat Special Zone was again the operating area for the “Iron Butterfly,” the symbol of River Division 593 worn proudly on the right shoulder of every man in the division. There was no canal, no waterway, no corner of the Rung Sat Special Zone that the “Iron Butterfly” did not patrol in its relentless search and pursuit of the enemy. Another member of the division was KIA during this time. Petty Officer D.L. Tucker went down in a firefight on 6 Jul. Many other crewmen were wounded in countless actions against the enemy and the legend of the “Iron Butterfly” grew.


On 4 July 1969 River Division 593 once again received orders to move its base of operations. This time it was assigned duty in direct support of the U.S. Army 1st Infantry Division and the 5th Division of the Army of the Republic of South Viet-Nam on the upper Saigon River, where already strong traditions and legends would be built on, strengthened and renewed in the months ahead.

The “Iron Butterfly” showed her colors on both the Saigon and the Thi Tinh Rivers, and the close proximity of this operating area to the large enemy complex in the tunnels of Cu Chi more than guaranteed the division plenty of action.

The division remained in this area on joint and combined operations from 4 Jul to 26 Sep 69 and the results of the division efforts, as noted by Commander Naval Forces Viet-Nam and his Vietnamese counterpart, were astronomical. Over 200 enemy soldiers were KIA by division patrols. Several tons of enemy supplies, including many very important documents, were captured. Several major enemy offenses against the strategic bridge at Phu Coung were stopped before they could reach the area by division night waterborne guard posts. One of these efforts was perhaps the longest firefight engaged in by any naval unit during the war. This all-night action was led by the legendary Chief Bob Monzingo, the Iron Butterfly’s own rogue warrior, in the middle of September and resulted in several enemy dead and numerous supplies captured.

On 15 Sep, an eight-boat patrol left Phu Cong en route to support a company of the 101st Airborne. It was ambushed prior to making its scheduled link-up with the Army company. Several men on the lead boats, along with the Division Commander, Lt. Bissonnette, were wounded. One boat had over 50 holes in it from enemy fire. Although the patrol had to stop long enough to dust-off the wounded after suppressing enemy fire, the operation proceeded as planned. Lt. Bissonnette refused to be evacuated with the rest of the wounded until the mission was complete.

Because of the constant contact with the enemy, everyone in the division was looking a bit haggard and needed a rest. A sigh of relief was heard by everyone when, on 26 Sep, the division was moved back to Nha Be and the Rung Sat Zone because, even as bad as the area was, it was not nearly as bad as being on the upper Saigon.

This stay in Nha Be would be very short-lived; the division was back in Phu Coung in November 1969 working with several local Army units and patrolling the river night and day. In December ’69 Lt. Bissonnette was relieved by Lt. Alan Deroco, who was 593’s third commander. . . and its last.

Two more men of the division were killed in action during this stay on the upper Saigon. FN N.C. Estes was KIA on 17 Jan 70 and Gunnersmate Seaman Frank Jacaruso was killed on 12 Mar 70. He was also the last.

After another brief stay in Nha Be, the division was ordered to the Cambodian border to lead the American assault across. During April and into June of 1970 the division operated off of the USS Benewa (APB 38) and the YRBM-20 anchored in the Bassac River.

593 had been an active participant in the Vietnamese turnover program, ordered by Commander Naval Forces Viet-Nam and had received its first 11 Vietnamese sailors for training back on 26 Mar 69. In the 15 months that followed, over 100 Vietnamese sailors were trained by and fought alongside their American counterparts and friends of the “Iron Butterfly.”

On 30 June 1970 at Chau Doc, alongside the USS Benewa on YRBM-20, River Division 593 was turned over to the Vietnamese Navy. So ended the name with the lowering of the last American flag. . . but not the legend.


During its short 26 month history, over 200 men served in River Division 593 — all of them volunteers and all of them professionals. Seven courageous men of River Division 593 lost their lives while serving in Viet-Nam. Personnel of the “Iron Butterfly” were in action much of the time, and were decorated often. Medals received by division personnel included one Navy Cross, at least eight Silver Stars, more than 60 Bronze Stars, over 50 Navy Commendation Medals, more than 20 Navy Achievement Medals, over 10 Vietnamese Crosses of Gallantry, and close to 100 Purple Hearts.

Editor’s note: River Division 593 got its name “Iron Butterfly” from their shoulder patch designed to look like a California Condor. The “Navy Times” had written an article about River Division 593 and in it referred to the unit as the “Iron Butterfly.” Because they were in the news quite often, the name stuck.