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| Landing Ship, Medium (LSM) | |
|---|---|
| Name | Landing Ship, Medium |
| Caption | USS LSM-45 off San Diego, 1944 |
| Country | United States |
| Type | Amphibious warfare ship |
| In service | 1944–1970s |
| Displacement | 520–1,095 tons (light–full) |
| Length | 203 ft 6 in (62.0 m) |
| Beam | 34 ft 6 in (10.5 m) |
| Draft | 7 ft 2 in (2.2 m) (light) |
| Propulsion | Diesel or steam engines, twin screws |
| Speed | 13–15 kn |
| Complement | 54–90 |
| Boats | Landing craft, vehicles, cargo |
Landing Ship, Medium (LSM) Landing Ship, Medium vessels were a class of United States amphibious transport ships built during World War II to carry vehicles, cargo, and troops directly onto unimproved beaches. Designed to bridge capability between the Landing Craft Infantry and Landing Ship, Tank classes, LSMs supported campaigns across the Pacific War, served in the Korean War and Vietnam War, and were transferred to allied navies including Royal Navy auxiliaries and several Republic of Korea Navy units.
LSM development began within the United States Navy Bureau of Ships and the United States Maritime Commission in response to operational lessons from the Guadalcanal Campaign, Solomon Islands campaign, and North African campaign. Designers borrowed features from LST-1-class tank landing ship hull forms and from diesel-powered Victory ship and Liberty ship construction practices employed by Newport News Shipbuilding, Federal Shipbuilding and Drydock Company, and Bath Iron Works. Naval architects incorporated a bow ramp and shallow draft for beaching similar to concepts trialed in Operation Torch landings and the Dieppe Raid studies. The propulsion choices—General Motors diesel or steam turbines—reflected industrial capacity constraints managed by Maritime Commission contracts and influenced by policy decisions from Franklin D. Roosevelt administration procurement.
From 1944–1946 over 500 LSMs were ordered and produced by yards including Brown Shipbuilding, Dravo Corporation, Ingalls Shipbuilding, Kaiser Shipyards, Moore Dry Dock Company, and Samuel Moore & Company. Production variants were differentiated by engineering plants and minor hull modifications and sometimes received class designations when transferred to allies, such as units redesignated under United States Coast Guard or sold to the French Navy, Royal Australian Navy, and Philippine Navy. Shipbuilding schedules were coordinated with the War Production Board, and hull numbers were allocated sequentially under Naval Registry Identification Number conventions. Postwar drawdowns led to many being laid up in the National Defense Reserve Fleet at James River Reserve Fleet and Suisun Bay Reserve Fleet.
LSMs first saw combat in Pacific island campaigns, supporting amphibious assaults during Battle of Peleliu, Battle of Iwo Jima, Battle of Okinawa, and logistical operations in the Gilbert and Marshall Islands campaign. Crews worked alongside units from the United States Marine Corps and United States Army during assaults planned by Admiral Chester W. Nimitz and amphibious doctrine influenced by Admiral Richmond K. Turner. In the Korean War several LSMs provided beach resupply and evacuation services during Battle of Inchon, while in the Vietnam War modified LSMs served as patrol, logistics, and mobile support platforms operating from bases such as Da Nang and collaborating with Military Assistance Command, Vietnam. Many ex-US LSMs remained active in postwar regional navies, participating in events from the First Indochina War to patrol duties in the South China Sea and interoperability operations with Southeast Asia Treaty Organization partners.
Conversion programs produced specialized variants: command ships modified like some units assigned to Naval Amphibious Forces, rocket-launching conversions supporting shore bombardment for operations akin to Operation Forager, and hospital or repair variants used in forward areas during World War II. Postwar conversions included survey ships, mine warfare auxiliaries, and civilian ferries sold to operators between Mediterranean Sea and Pacific Islands. Several were transferred under Mutual Defense Assistance Program terms to navies including Japan Maritime Self-Defense Force, Italian Navy, Royal Thai Navy, Indonesian Navy, and South Vietnamese Navy where they were further modified for riverine and coastal roles during conflicts such as the Indonesia–Malaysia confrontation and the Vietnam War.
Standard LSM armament was light and intended for self-defense: twin and single mounts of Oerlikon 20 mm cannon and twin Bofors 40 mm gun installations in configurations influenced by wartime supply from the United Kingdom and domestic production by General Motors subsidiaries. Radar and radio suites varied by yard and refit, using systems supplied by firms like Radio Corporation of America and Western Electric, with additions of fire-control directors retrofitted during service. Some rocket-launching conversions mounted multiple rocket launchers patterned after T16 Multiple Rocket Launcher concepts used in amphibious preludes to landings.
Crew complements ranged from about 54 to more than 90 depending on role and wartime modifications; enlisted personnel crews often included sailors transferred from Gunnery Schools and Net and Boom Defense units. Habitability reflected wartime expedience: berthing compartments, a small galley and medical bay arranged per standards of the United States Naval Hospital guidance, and cargo handling gear compatible with LVT amphibious tractors and early DUKW truck-boat hybrid operations. Training for crews included amphibious doctrine from Naval Amphibious Base Coronado and schools influenced by instructors who served in Amphibious Corps, Pacific Fleet operations.
A limited number of LSMs survive as museum ships and memorials in institutions such as the National Museum of the Pacific War-affiliated collections, regional maritime museums, and memorial parks in the United States, Australia, and France. Preservation efforts are supported by veterans' groups associated with Veterans of Foreign Wars, American Legion, and local historical societies; restoration challenges include corrosion addressed through programs modeled on National Historic Preservation Act partnerships and fundraising via grants from cultural institutions and foundations that have supported naval preservation. Surviving units are studied by maritime historians from universities including United States Naval Academy, Georgetown University, Columbia University, and technical analyses published in journals tied to Smithsonian Institution research initiatives.
Category:Amphibious warfare vessels of the United States Navy