Succeeding them following the Korean Armistice was Mine Division – 111 which had almost totally converted to 50′ Motor Launch Minesweepers, heavily modified by Ship Repair Depot in Sasebo with decks, some with enclosed pilot houses and masts. They were forced by Navy wisdom to relinquish their MSB designations (Mine Sweeping Boats) and reclassify their boats as Motor Launch Mine Sweepers – MLMS. This was due to BuShips having given the MSB designation to a new 57′ minesweeper class they were developing.

In 1958 these boats were replaced by newly built 36′ Mine Sweeping Launches (MSL’s), powered by Boeing Gas Turbine Type 502-10C. Twenty MSL’s were delivered to WestPAC split between Sasebo and Long Beach, CA. Following this re-organization their LCVP’s and MLMS’s were given to Taiwan, Korea, and Vietnam. The Division was re-named Mine Division – 33, and in 1961 the USS Epping Forest LSD-4, was transferred to MinFlot 1 in Sasebo and re-designated MCS-7. Mine Countermeasures Support ship.

In August 1966 MinDiv – 33 was decommissioned and tranferred aboard the USS Epping Forest mCS-7 as the Boat Division. In Fall of 1968 the USS Epping Forest was de-commissioned. The Boat division was sent to the Sasebo Seawall for the winter. The following Spring the USS Catskill MCS-2 arrived in Sasebo as the new mothership. During which in the waning budgets due to Vietnam, the Catskill was decommissioned. Minesweeping Boat Divisions homeported in Sasebo no longer exist.

Three minute introduction only. WP limits videos to 32mB

This movie, The Small Boat Navy, was sent to me by a shipmate in 2013. It appears to be a very well done documentary, post 1968, regarding Vietnam Naval Coastal Surveillance and Riverine Warfare. There is a section devoted to minesweeping the Long Tau Shipping Channel (Saigon River Complex)using 57′ Mine Sweeping Boats – MSB’s. Nothing is mentioned regarding the 36′ Mine Sweeping Launches – MSL’s of Mine Division – 33 transported by the USS Epping Forest MCS-7 Who arrived in July 1964 for the  check sweeping of Cam Ranh Bay, Nha Trang Harbor, and Da Nang Harbor. The EF MCS-7 transported our ten MSL’s to Vietnam eighteen times through 1968. Our XO of MinDiv – 33 said he attended a meeting in early 1966 in Saigon, where MACV was considering our 36′ Mine Sweeping Launches for the Long Tau Shipping Channel minesweeping effort. MSL’s were eliminated in favor of the 57′ MSB’s due to the MSB’s larger size, pilot house, bunk arrangements, head facilities, and general sea worthiness. Also, the MSB was fitted with ceramic armor, and had a small crane for deploying oropesa minesweeping gear, and the newly designed chain drag sweep gear, for clearing command detonated mine wires from river shorelines to mines planted in the river.

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Edward Sinclair

This video shows Mine Sweeping Boat Division ONE launching Four LCVP Magnetic Minesweepers from the USS Cabildo LSD-16 in April 1952. MSB-1 had a variety of boats, including modified USN Motor Launches (40′ and 50′), and 36′ Landing Craft Vehicle Personnel (LCVP’s) outfitted with Oropesa sweep gear for moored minesweeping. The four LCVP’s outfitted for magnetic minesweeping could not be launched by cranes from the LSD, because the magnetic minesweeping gear was powered by several 750 lb submarine batteries stored in the boat, making it too heavy to launch via the mother ship’s cranes. Therefore, the LSD would ballast down, flooding a portion of the well deck, and the boats would simply sail out via the stern gate. Recovering magnetic boats at night, were the reverse of the process. The LSD ballasted down, flooding the well deck with enough water to float the boats, and the boats would sail into the well deck under their own power.

The magnetic minesweeping tails were approximately 1,500 feet long, with bare electrodes hanging into the water at 1,000 and 1,500 feet, alternately pulsed positive and negative, setting up large and powerful magnetic fields to detonate magnetic mines 1,000+ feet behind the towing boats. This of course was predicated that the minesweepers be as non-magnetic as possible, because they first had to sail past these magnetic ground mines lying on the bottom of the harbor.

The video shows the boats connecting to their mag tails, retrieved from these same boats using sailor-power (by-hand) following the previous days sweep operations and “flaked-down” on the well deck.

Following the magnetic mine sweeping boats, there is an LCVP moored minesweeping boat shown cutting a moored mine. Following the severing of a moored mine cable or chain, the mines float to the surface, and generally are sunk from a safe distance away by gunfire. However, in this video you see two Mine Squadron Three Explosive Ordnance Disposal Officers in a rubber dinghy paddling to these Russian made mines, and disarming then (Rendering Them Safe) for the purpose of exploiting the technology and returning then to EOD Headquarters located in Indian Head, MD during the Korean War. Generations of EOD Divers have been trained to disarm live mines on the dozens of Russian mines captured by Mine Squadron Three Officers in Wonsan, North Korea during our 900 day seige and occupation of this enemy harbor.

In fact, one of these 1,200 lb Russian MKB behemoths was discovered floating down the Long Tao Shipping Channel (Saigon River) on December 31, 1966, and the EOD Diver LtCdr Frank Talarico disarmed the MKC Chemical Horn Mine in the river near the Saigon Port Complex. He tied a rope to an eyebolt in the mine and dagged it to shallow water, he and another EOD person removed the cover plate, and pulled out the detonator and Tetryl booster. Their training at Indian Head kept them alive. The 506 lbs of cast TNT is later steamed out of the 984 lb steel case to for return to EOD HQ.

I apologize for the abrupt end to the video. Evidently, the hosting service truncated the video due to it;s size.

Ed Sinclair

A second major discovery in the use of Russian mines by the enemy in Vietnam, the North Vietnamese hauled segments of the more modern Russian ground mines, the 24″ cylindrical HAT II acoustic-magnetic bottom mines down the Ho Chi Minh Trail, to the Cua Viet River. These have modular sections, and are up to 6 ft long when assembled. One was believed to have exploded and capsized an LCU/YFU full of munitions, killing six of the seven sailors aboard, while traversing the Cua Viet River to the Dong Ha Marine Base upriver.

EOD Divers found another HAT II fully assembled and planted outside the bar at the mouth of the Cua Viet river, and rendered it safe. Luckily, no large USN ships could navigate the shallow Cua Viet River, and did not venture across the bar heading upriver.

It is believed that the North Vietnamese, or like during the Korean War, Russian advisors, assembled these mines, and tied a series of floation devices around or alongside them, swam into the river floating these mines, and deflating the flotation devices with knives to “plant” these ground mines on the river bottom. These mines were believed to have acoustic-magnetic trigger mechanisms.

During the Battle Of Dai Do Village, in the Sring of 1968, Naval forces battling the NVA north of the Cua Viet river spotted suspicious activity on the north bank during the battle, and sent ground troops to investigate later. They discovered segments of these HAT II cylindrical mines on the river bank. EOD divers from the Cua Viet Base discovered parts for eight complete mines, evidently hauled down the Ho Chi Minh Trail in peices by the North Vietnamese. This was the NVA attempt to close down the Dong Ha-Cua Viet ammo supply line, and overrun the USMC Base at Dong Ha. MSL’s from the USS Epping Forest left Da Nang the day this discovery was made, and sailed north to Cua Viet, prepared to sweep the river. This minesweeping unit consisting of ten 36′ Mine Sweeping Launches, now designated as the Epping Forest Boat Division, formerly Mine Division 33, had moved aboard the USS Epping Forest permanently in the summer of 1966. They allegedly towed a WWII “iron rail” magnetic sweep, believed to be a section of magnetized railroad track, packed inside a PVC pipe, behind their 36′ Mine Sweeping launch. No detonations resulted from their sweeps of the Cua Viet, the scene of the deadly LCU/YFU explosion days earlier.

Almost all remaining mine planting activity in Vietnam in Bays and Rivers consisted of home made explosive devices, manufactured in the jungle from unexploded US ordnance explosives, trash, and battlefield junk such as tin cans, shell casings, aircraft wing tanks, and various containers. The most frequent were command detonated explosives planted in the rivers, and detonated by an enemy fighter from a foxhole alongside the river, using dry cell batteries.

View MSL video here produced by the USN in 1959. this is one of a series of four videos produced by the Navy covering 36′ Mine Sweeping Launches for assault minesweeping in Rivers, 57′ Mine Sweeping Boats as Harbor and Channel Minesweepers, 145′ Mine Sweeper Coastal, and 172′ Mine Sweeper Ocean. These are all wooden hulled vessels specifically designed from experiences in the Korean War losing steel-hulled minesweepers to Russian magnetic mines.