The Maritime Unit (MU) was a branch of the

Office of Strategic Services The Office of Strategic Services (OSS) was the first intelligence agency of the United States, formed during World War II. The OSS was formed as an agency of the Joint Chiefs of Staff (JCS) to coordinate espionage activities behind enemy lines ...

that enabled maritime warfare for the allies during

World War II World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...

. MU's mission was to "infiltrate agents and supply resistance groups by sea, conduct maritime

sabotage Sabotage is a deliberate action aimed at weakening a polity, government, effort, or organization through subversion, obstruction, demoralization (warfare), demoralization, destabilization, divide and rule, division, social disruption, disrupti ...

, and to develop specialized maritime

surface A surface, as the term is most generally used, is the outermost or uppermost layer of a physical object or space. It is the portion or region of the object that can first be perceived by an observer using the senses of sight and touch, and is ...

and subsurface equipment and devices." MU developed specialized

boat A boat is a watercraft of a large range of types and sizes, but generally smaller than a ship, which is distinguished by its larger size or capacity, its shape, or its ability to carry boats. Small boats are typically used on inland waterways s ...

s, equipment, and explosives, fashioned underwater breathing gear, waterproof watches and

compass A compass is a device that shows the cardinal directions used for navigation and geographic orientation. It commonly consists of a magnetized needle or other element, such as a compass card or compass rose, which can pivot to align itself with No ...

es, an inflatable motorized surfboard, and "a two-man

kayak ] A kayak is a small, narrow human-powered watercraft typically propelled by means of a long, double-bladed paddle. The word ''kayak'' originates from the Inuktitut word '' qajaq'' (). In British English, the kayak is also considered to be ...

that proved so promising that 275 were ordered by the British." MU was originally established as a division of the Special Operations Branch of the OSS but was granted Branch status on June 10, 1942. The

Frogmen A frogman is someone who is trained in scuba diving or swimming underwater. The term often applies more to professional rather than recreational divers, especially those working in a tactical capacity that includes military, and in some Europea ...

of the MU are considered pioneers of amphibious, maritime, and underwater warfare. While it was a civilian agency, the

United States Navy SEALS The United States Navy Sea, Air, and Land (SEAL) Teams, commonly known as Navy SEALs, are the United States Navy's primary special operations force and a component of the United States Naval Special Warfare Command. Among the SEALs' main func ...

state clearly that the OSS Maritime Unit is one of their direct preceding organizations. Underwater combat swimmer of the Office of Strategic Services Detachment 404 Maritime Unit

Underwater combat swimmer of the Office of Strategic Services Detachment 404 Maritime Unit

MU planned and carried out the amphibious phases of OSS activities and assisted in the development of the special equipment required. If operations included water, the shoreline, coastal areas, or water approaches, then MU techniques were used. Those techniques were clandestine ferrying, maritime sabotage, and beach and hydrographic reconnaissance. The last living Frogman of the OSS was Henry “Hank” Weldon.

Organizational structure

Field bases were located away from headquarters. MU FIELD BASE ORGANIZATION

Headquarters was located in

Washington, DC Washington, D.C., formally the District of Columbia and commonly known as Washington or D.C., is the capital city and Federal district of the United States, federal district of the United States. The city is on the Potomac River, across from ...

MU PLANNING AND ADMINISTRATION IN WASHINGTON

Inventions

The

Lambertsen Amphibious Respiratory Unit The Lambertsen Amphibious Respiratory Unit (LARU) is an early model of closed circuit oxygen rebreather used by military frogmen. Christian J. Lambertsen designed a series of them in the US in 1940 (patent filing date: 16 Dec 1940) and in 1944 ( ...

(LARU) was developed by Christian J. Lambertsen, a captain in the US Army assigned to the MU.

References

{{Authority control Research and Analysis Branch 1942 establishments in the United States 1945 disestablishments in the United States Agencies of the United States government during World War II Defunct United States intelligence agencies Government agencies disestablished in 1945 Government agencies established in 1942 Intelligence services of World War II World War II espionage