U.S. Navy

Net Laying Ships (AN)

Net laying ships installed, maintained, and recovered anti-torpedo and anti-submarine nets that guarded harbor entrances across every theater of World War II. Named for trees, plants, and wood species, these unsung vessels ensured that no anchorage went unprotected after the lessons of Pearl Harbor - where the torpedo net had been left open on the morning of December 7, 1941. From Ulithi to Scapa Flow, AN ships were often among the first to arrive at captured bases, stringing steel curtains beneath the surface before the fleet could safely anchor.

World War II - Harbor Defense 1941 - 1945

Pearl Harbor - Torpedo Nets

December 7, 1941

On the morning of the attack, the torpedo net protecting the Pearl Harbor entrance had been opened for routine ship traffic - leaving the anchorage exposed. After December 7, the Navy mandated anti-torpedo nets at every major anchorage worldwide, and AN-class net laying ships became critical to harbor defense for the rest of the war. Read more

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Tree-Class Net Laying Ships

AN-1 through AN-37

First Commissioned

The earliest net layers, converted or purpose-built 1941-1943, named for common North American trees. These ships strung the first harbor defense nets across anchorages from Iceland to the South Pacific - Ash, Beech, Birch, Buckeye, Elm, and dozens more. They arrived at newly captured bases before the fleet, rigging steel curtains beneath the surface so ships could anchor safely. Read more

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Ailanthus-Class Net Laying Ships

AN-38 through AN-56

First Commissioned

Primary Theater

Wooden-hulled vessels built 1943-1944, designed from the keel up for net laying operations. The Ailanthus-class carried heavier net-handling gear than earlier conversions and served across the Pacific theater securing forward anchorages at Eniwetok, Ulithi, and Leyte Gulf. Read more

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Aloe-Class Net Laying Ships

AN-57 through AN-77

The largest class of purpose-built net layers, launched 1944-1945. Aloe-class ships were among the first support vessels to arrive at newly captured bases in the Pacific, rigging harbor defenses before fleet anchorages were established. Named for plants and trees from tropical and subtropical regions. Read more

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Post-War & Cold War 1945 - 1960s

Cohoes-Class Net Laying Ships

AN-78 through AN-92

Extended Service

Steel-hulled net layers built 1944-1946, designed for greater endurance and open-ocean operations. The Cohoes-class represented the final evolution of the AN type, with several ships continuing in Cold War service for harbor defense and minesweeping support duties into the 1960s. Read more

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89+

Net Laying Ships

4

Ship Classes

Trees

Naming Convention

Harbor

Defense Mission