page_title: Underway replenishment
section_title: Operational use
hierarchical_section_title: Underway replenishment / History / Operational use
caption_attribution_description: English: The U.S. Navy fleet oiler USS Maumee (AO-2) off the Norfolk Naval Shipyard, Virginia (USA), on 31 March 1945. She is painted in Camouflage Measure 12.
context_page_description: Replenishment at sea or underway replenishment is a method of transferring fuel, munitions, and stores from one ship to another while under way. First developed in the early 20th century it was used extensively by the United States Navy as a logistics support technique in the Pacific theatre of World War II, permitting U.S. carrier task forces to remain at sea indefinitely.
context_section_description: In 1916 Chester Nimitz, executive officer and chief engineer of the United States Navy  oiler USS Maumee, while the ship was stationed in Cuba, designed and jerry-rigged a riding-abeam refueling system with ship booms supporting rubber hoses between the oiler and the receiving destroyer with the assistance of G. B. Davis, Matt Higgins and Lieutenant F. M. Perkins. The system employed a 10 in (250 mm) towing hawser, two 6 in (150 mm) breast lines to prevent the rupture of the refueling hose between the two vessels, and  50 ft (15 m) lengths of 4-inch-diameter (10 cm) rubber fuel hose. As well a fuel pump was used to speed up the transfer of fuel.
  Following the declaration of war, 6 April 1917, USS Maumee was assigned duty refueling at sea the destroyers being sent to Britain. Stationed about 300 miles south of Greenland, Maumee was ready for the second group of six U.S. ships to be sent as they closed on her on 28 May 1917. Following this first deployment, she transferred fuel to 34 destroyers over the course of a three-month period. These fuel transfers were made with only a 40 ft (12 m) separation between the moving ships. With the fueling of those destroyers, Maumee pioneered the Navy's underway refueling operations, thus establishing a pattern of mobile logistic support which would enable the Navy to keep its fleets at sea for extended periods, with a far greater range independent of the use of a friendly port.
  While during the interwar period most navies pursued the refueling of destroyers and other small vessels by either the alongside or astern method, it was the conventional wisdom that larger warships could neither be effectively refueled astern nor safely refueled alongside, until a series of tests conducted by now-Rear Admiral Nimitz in 1939–40 perfected the rigs and shiphandling which made the refueling of any size vessel practicable.
  This was used extensively as a logistics support technique in the Pacific theatre of World War II, permitting U.S. carrier task forces to remain at sea indefinitely. Since it allowed extended range and striking capability to naval task forces the technique was classified so that enemy nations could not duplicate it.
  In the 1950s and 1960s the U.S. Navy developed a multi-product supply ship that could deliver fuel, ammunition and stores while underway. These ships saw the introduction of a transfer system using a ram tensioner that keeps the highline between the ships tensioned, allowing for smooth transfer, as well as taking into account any movement of the ships. Over time this method evolved into the Standard Tensioned Replenishment Alongside Method (STREAM). The U.S. Navy also uses the spanwire rig, bye close-in rig, and spanline rig to transfer.  The STREAM rig is preferred over other connected replenishment methods as it permits a greater separation between the ships.
  Germany used specialized submarines (so-called milk-cows) to supply hunter U-boats in the Atlantic during WWII. These were relatively ponderous. They required both submarines to be stationary on the surface, took a long time to transfer stores, and needed to be in radio contact with the replenished boat, making them easy targets. Due to this, those not sunk were soon retired from their supply role.
  Although time and effort has been invested in perfecting underway replenishment procedures, they are still hazardous operations.
  Presently, most underway replenishments for the U.S. Navy are handled by the Military Sealift Command.  It is now used by most, if not all, blue-water navies.
caption: The USS Maumee (AO-2) oiler achieved the first operational UR in 1917.
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