Antisubmarine Operations

Insofar as future warfare was concerned, the most important naval developments of World War II may have occurred in the North Atlantic, where the struggle for survival of Great Britain was won before the United States offensive in the Pacific began. The victory over the German submarine was mainly the result of British efforts, the United States contribution consisting primarily of mass production processes.

Karl Doenitz (Donitz), the German admiral in command of submarines, was one of the toughest naval antagonists that the Allies met during the war. He believed that Germany could win only by sinking an average of 750,000 tons of Allied shipping monthly, and his strategy was to keep his submarines moving to areas where sinkings were easiest to obtain. Against convoys he preferred to use heavy concentrations of Uboats known as wolf packs in continuous attacks, directing them individually from his headquarters ashore. The weakness in this method of control was the amount of two-way radio traffic required: Allied high frequency direction finders were able to locate German submarines with considerable accuracy. Wider convoy routing and better antisubmarine precautions in distant areas forced Doenitz to return to the shipping lanes of the North Atlantic, and it was there that the battle was finally settled in the summer of 1943.

The German submarines were defeated by the Royal Navy’s battle-scarred escorts and by aircraft of the Royal Air Force (RAF) Coastal Command under the operational control of the Admiralty. British scientists also made contributions to this victory, two of them major: microwave radar and operational research on antisubmarine warfare methods. The British success can be attributed to radar; sonar (asdic in British terminology), high frequency direction finding; the escort carrier; antisubmarine support groups of destroyers, which reinforced the escorts of convoys under attack; and the extension of landbased airpower across the Atlantic by the employment of B-24 Liberators. The principal United States contribution was the escort carrier, used to cover the areas in the mid-Atlantic that landbased aircraft did not reach. Escort groups, consisting of a small carrier and about 4 destroyer types, began operating in June 1943. They were especially successful in locating submarine refueling rendezvous. Hunter-killer groups of this type are still retained in the operating forces of the United States Navy.

The technological advance that proved most fruitful for the British in the antisubmarine campaign was microwave radar. German submarines while on the surface were able to detect enemy use of long-wave radar and could submerge in time to avoid attack. They failed, however, to discover that microwave radar was being employed against them until 1944, with the result that surface vessels were able to approach close enough to a submarine before it submerged to get it on the sonar. Coastal Command aircraft were eventually fitted with this type of radar. Used in conjunction with the Leigh light, a powerful searchlight controlled by the radar set, it was able to surprise surfaced submarines, which could be attacked before they submerged.

Late in the war antisubmarine ordnance was radically improved by the introduction of a projectile to augment the depth charge. The mount, called a hedgehog, threw 24 missiles over the bow of the attacking ship. Since the missiles exploded only after one of them had struck the submarine, there was no explosion in an unsuccessful attack to disturb the sonar search and give the submarine time to escape.

Because sailing in convoys delayed shipping, vessels capable of making 15 knots and over sailed singly, with the expectation that faster turnarounds would compensate for submarine losses. Pressure was brought on the Admiralty to sail 13-knot ships singly as well, but this change proved a mistake, and the 13-knot convoys were reestablished in May 1941.

Improved convoy efficiency was finally attained through operational research. By analytical studies of attacks, British scientists discovered that the number of sinkings bore no relation to the size of the convoy and depended only on the number of attacking U-boats, on whether the convoy had air escort, and, when it did not, on the number of surface escorts. Convoys were therefore increased in size from 32 to 54 ships, providing both better protection and faster delivery of cargoes. Air escort during daylight was found to decrease losses by an additional 64 percent, making sinkings negligible.

Late in the war the Germans developed the snorkel, by which a submarine could both cruise and charge batteries underwater with only the extension of this breather pipe exposed. It was perfected too late to affect the German submarine effort and require antisubmarine methods to counter it. But the problem of countermeasures remained with the postwar nuclear-powered submarine, a true submersible able to remain underwater constantly and cruise at great depths with high speed.

Amphibious Forces

All ground operations in World War II began with amphibious assaults. The first, made in August 1942 at Guadalcanal, was a defensive operation designed to seize the island in order to halt the Japanese thrust into the Solomons. It was followed. in November by landings in North Africa. Amphibious operations in Europe included the assault on Sicily in July 1943, the cross-Channel invasion of Normandy in June 1944, and the movement into southern France in August. These were all primarily operations intended to seize beachheads from which large forces would subsequently break out for land campaigns. In the Pacific, however, one amphibious operation necessarily followed another. Amphibious operations in the Southwest Pacific were made at frequent intervals in relatively short shore-to-shore movements, while in the Central Pacific they involved large lifts over long distances. The assaulting forces in Europe were Army troops, whereas in the Central and Southwest Pacific both Marine and Army forces were employed. A greater amount of improvisation was necessary in the Southwest Pacific than in the Central Pacific, since naval elements were smaller and the theater generally received lower priorities for amphibious equipment.

Because of sound doctrine and proper landing equipment, all United States amphibious operations in World War II were successful. The doctrine had been developed by the United States Marine Corps in the two decades before the war, under the shadow of the British failure at Gallipoli in World War I. It was set forth in a Manual for Landing Operations, which attempted to define (1) command relationships; (2) naval gunfire support; (3) air support; (4) ship-toshore movement; (5) the securing of the beachhead; and (6) logistics. The basic doctrine outlined in this manual withstood the long trial by fire in war without fundamental changes.

The reason for this success was without doubt the provision of adequate craft for the landing of assault units and for logistic support over the beaches until proper port facilities could be built. The landing craft were of two basic types: (1) ships and boats that had the ability to beach without swamping, and also to withdraw; and (2) amphibians. Hulls of the first type were designed so that the craft grounded on only a small area forward. In withdrawing, the slipstream from the protected propeller washed away sand in the grounded area, thus releasing the craft from the beach. A ramp forward facilitated the rapid discharge of passengers and cargo. The smaller types, which were carried aboard transports, were designed by Andrew J. Higgins, a New Orleans boatbuilder. These were the LCVP (landing craft, vehicle and personnel) and the LCM (landing craft, medium), which were capable of transporting a tank. A larger type, designed to proceed under its own power to the designated area, was of British design; it included the LST (landing ship, tank) and the LCI (landing craft, infantry). The LCI subsequently evolved into a close-support gunboat type, while the LST with its ample tank deck became one of the most useful crafts in the war, employed in a range of logistic services far beyond those originally intended. LST’s were employed as hospital ships, barrack ships, tenders for small landing craft, floating machine shops, and issue ships. When they were forced to beach out from the shoreline because of shallow gradients, they could carry pontoon causeways with them. Intermediate types between shipboard craft and the LST were the LSM (landing ship, medium), a small LST, and the LCT (landing craft, tank), which was essentially a powered barge.

The second basic type of landing vehicle, the amphibian, could be propelled both in water and on land. The caterpillar type, invented by Donald Roebling, was able to cross the shoals and beaches of the Pacific. Two models were employed: the personnel carrier, LVT (landing vehicle, tracked), with a ramp in the rear, which allowed troops to debark quickly under some cover; and the LVT (A), or armored amphibian, which was actually an amphibious tank. The Army developed a vehicle of its own, code named the DUKW, an amphibious truck with a propeller drive in the water and a wheeled drive on land.

Special types of large amphibious ships also were built, mainly for the transport and support of landing craft, such as the LSD (landing ship, dock) and the LSV (landing ship, vehicle), an amphibian carrier. The assault transport or cargo ship carried as many as 9 LCM’s and 26 LCVP’s.

An important element in an amphibious operation was the shore party, which included the labor for quick unloading under difficult conditions. In the Central Pacific, where troop space in large overwater movements was limited, such labor was performed by a small number of specialized service troops augmented by reserves, although the latter were often called into combat when the unloading phase was at its most critical stage. In the Southwest Pacific the engineer special brigade was employed; it had regiments consisting of a boat battalion and a shore battalion, ably officered and with needed service troops attached.

Task Force System

During World War II the expression “task force” used in connection with fast carrier operations in the Pacific caught the imagination of the American people and became part of their language, though with a variety of meanings. In the working language of the United States Navy, however, “task force” is one of a group of terms employed in connection with a system of organization which it has evolved for managing its combat ships in order to make the most effective use of sea and air in modern, fast-moving warfare, while at the same time providing for te maintenance, support, and constant replenishment needed by these ships. In naval warfare it is the manned ship that fights, not the man himself. A combat ship functions only at sea, but it must return to port at various intervals to prepare and replenish itself again for sea duty. It is therefore possible to separate in time the tactical employment from the logistics of a ship, its operation from its administration, and this separation is carried over into naval organizational structure in a manner not possible in land warfare.

The task force method of conducting naval warfare is a byproduct of what might be called the task-type organization of naval operating forces. In this method of organization a combat ship’s captain actually works for two commanders. He is under the operational control of a task commander, who is responsible for completing some task within the Navy’s mission; and is under the administrative control of a type commander, who is responsible for the ship’s upkeep, supply, discipline, and (within certain limits) training. Broadly speaking, a task commander is concerned with functions of purpose, and he serves as operational commander of a composite force of ships suited to a particular purpose. A type commander is concerned with the functions of support, and he maintains the readiness of his ships, which are usually of one type, such. as carriers, cruisers, or destroyers. He is an administrative commander and does his job primarily with such of his ships as are in port.

The task force organization of combat ships was best represented during World War II by the carrier task forces, which also included battleships, cruisers, and destroyers. Amphibious task forces were composed of amphibious ships of all types, as well as battleships for gunfire support, small carriers for air support, and destroyer types for antisubmarine protection. Replenishment task forces consisted primarily of tankers, ammunition ships, and salvage tugs, with a cruiser flagship and small carriers and destroyer types for protection. These task forces could be divided into task groups and task units, while the administrative commands retained the older designations of squadron and division. The task concept was expanded to the fleet level in 1944. The two task fleets in the Central Pacific were the Fifth and Third fleets: the Fifth Fleet conducted the operations against the Marianas, Iwo Jima, and Olcinawa, while the Third Fleet assisted Gen. (later General of the Army) Douglas MacArthur in the recapture of the Philippines. The units that composed these fleets came from the pool of Central Pacific ships, which were assigned or withdrawn as operations required and the condition of the individual ships warranted. When ships were withdrawn from operational status, they reverted to the control of their type commander, whose headquarters were usually located with that of the commander of the Pacific Fleet. Ships newly commissioned or reverting to operational status after extensive repairs were assigned temporarily by the type commander to training commands, which specialized in preparing ships for combat. Such training was usually conducted outside of operational areas, although Japanese forces on bypassed Pacific islands provided targets for aircraft training.