A convoy is a group of vehicles motor vehicles or ships, traveling together for mutual support and protection. A convoy is organized with armed defensive support, it may be used in a non-military sense, for example when driving through remote areas. Arriving at the scene of a major emergency with a well-ordered unit and intact command structure can be another motivation. Naval convoys have been in use for centuries, with examples of merchant ships traveling under naval protection dating to the 12th century; the use of organized naval convoys dates from when ships began to be separated into specialist classes and national navies were established. By the French Revolutionary Wars of the late 18th century, effective naval convoy tactics had been developed to ward off pirates and privateers; some convoys contained several hundred merchant ships. The most enduring system of convoys were the Spanish treasure fleets, that sailed from the 1520s until 1790; when merchant ships sailed independently, a privateer could cruise a shipping lane and capture ships as they passed.
Ships sailing in convoy presented a much smaller target: a convoy was as hard to find as a single ship. If the privateer found a convoy and the wind was favourable for an attack, it could still hope to capture only a handful of ships before the rest managed to escape, a small escort of warships could thwart it; as a result of the convoy system's effectiveness, wartime insurance premiums were lower for ships that sailed in convoys. Many naval battles in the Age of Sail were fought around convoys, including: The Battle of Portland The Battle of Ushant The Battle of Dogger Bank The Glorious First of June The Battle of Pulo Aura By the end of the Napoleonic Wars the Royal Navy had in place a sophisticated convoy system to protect merchant ships. Losses of ships travelling out of convoy however were so high that no merchant ship was allowed to sail unescorted. In the early 20th century, the dreadnought changed the balance of power in convoy battles. Steaming faster than merchant ships and firing at long ranges, a single battleship could destroy many ships in a convoy before the others could scatter over the horizon.
To protect a convoy against a capital ship required providing it with an escort of another capital ship, at high opportunity cost. Battleships were the main reason that the British Admiralty did not adopt convoy tactics at the start of the first Battle of the Atlantic in World War I, but the German capital ships had been bottled up in the North Sea, the main threat to shipping came from U-boats. From a tactical point of view, World War I–era submarines were similar to privateers in the age of sail; these submarines were only a little faster than the merchant ships they were attacking, capable of sinking only a small number of vessels in a convoy because of their limited supply of torpedoes and shells. The Admiralty took a long time to respond to this change in the tactical position, in April 1917 convoys were trialled, before being introduced in the Atlantic in September 1917. Other arguments against convoys were raised; the primary issue was the loss of productivity, as merchant shipping in convoy has to travel at the speed of the slowest vessel in the convoy and spent a considerable amount of time in ports waiting for the next convoy to depart.
Further, large convoys were thought to overload port resources. Actual analysis of shipping losses in World War I disproved all these arguments, at least so far as they applied to transatlantic and other long-distance traffic. Ships sailing in convoys were far less to be sunk when not provided with an escort; the loss of productivity due to convoy delays was small compared with the loss of productivity due to ships being sunk. Ports could deal more with convoys because they tended to arrive on schedule and so loading and unloading could be planned. In his book On the Psychology of Military Incompetence, Norman Dixon suggested that the hostility towards convoys in the naval establishment were in part caused by a perception of convoys as effeminating, due to warships having to care for civilian merchant ships. Convoy duty exposes the escorting warships to the sometimes hazardous conditions of the North Atlantic, with only rare occurrences of visible achievement; the British adopted a convoy system voluntary and compulsory for all merchant ships, the moment that World War II was declared.
Each convoy consisted of between 30 and 70 unarmed merchant ships. Canadian, American, supplies were vital for Britain to continue its war effort; the course of the Battle of the Atlantic was a long struggle as the Germans developed anti-convoy tactics and the British developed counter-tactics to thwart the Germans. The capability of a armed warship against a convoy was illustrated by the fate of Convoy HX 84. On November 5, 1940, the German heavy cruiser Admiral Scheer encountered the convoy. Maiden, Kenbame Head and Fresno were sunk, other ships were damaged. Only the sacrifice of the Armed Merchant Cruiser HMS Jervis Bay and failing light allowed the rest of the convoy to escape; the deterrence value of a battleship in protecting a convoy was dramatically illustrated when the German light battleships Scharnhorst and Gneisenau, mounting 11 in guns, came upon an eastbound British convoy in the North Atlantic on February 8, 1941. When the Germans detected the slow but well-protected battleship HMS Ramillies escorting the convoy, they f
Oerlikon 20 mm cannon
The Oerlikon 20 mm cannon is a series of autocannons, based on an original German 20 mm Becker design that appeared early in World War I. It was produced by Oerlikon Contraves and others, with various models employed by both Allied and Axis forces during World War II, many versions still in use today. During World War I, the German industrialist Reinhold Becker developed a 20 mm caliber cannon, known now as the 20 mm Becker using the Advanced Primer Ignition blowback method of operation; this had a cyclic rate of fire of 300 rpm. It was used on a limited scale as an aircraft gun on Luftstreitkräfte warplanes, an anti-aircraft gun towards the end of that war; because the Treaty of Versailles banned further production of such weapons in Germany, the patents and design works were transferred in 1919 to the Swiss firm SEMAG based near Zürich. SEMAG continued development of the weapon, in 1924 had produced the SEMAG L, a heavier weapon that fired more powerful 20x100RB ammunition at a higher rate of fire, 350 rpm.
In 1924 SEMAG failed. The Oerlikon firm, named after the Zürich suburb of Oerlikon where it was based acquired all rights to the weapon, plus the manufacturing equipment and the employees of SEMAG. In 1927 the Oerlikon S was added to the existing product line; this fired a still larger cartridge to achieve a muzzle velocity of 830 m/s, at the cost of increased weight and a reduced rate of fire. The purpose of this development was to improve the performance of the gun as an anti-tank and anti-aircraft weapon, which required a higher muzzle velocity. An improved version known as the 1S followed in 1930. Three sizes of gun with their different ammunition and barrel length, but similar mechanisms, continued to be developed in parallel. In 1930 Oerlikon reconsidered the application of its gun in aircraft and introduced the AF and AL, designed to be used in flexible mounts, i.e. manually aimed by a gunner. The 15-round box magazine used by earlier versions of the gun was replaced by drum magazine holding 15 or 30 rounds.
In 1935 it made an important step by introducing a series of guns designed to be mounted in or on the wings of fighter aircraft. Designated with FF for Flügelfest meaning "wing-mounted", these weapons were again available in the three sizes, with designations FF, FFL and FFS; the FF fired a larger cartridge than the AF, 20x72RB, but the major improvement in these weapons was a significant increase in rate of fire. The FF weighed 24 kg and achieved a muzzle velocity of 550 to 600 m/s with a rate of fire of 520 rpm; the FFL of 30 kg fired a projectile at a muzzle velocity of 675 m/s with a rate of fire of 500 rpm. And the FFS, which weighed 39 kg, delivered a high muzzle velocity of 830 m/s at a rate of fire of 470 rpm. Apart from changes to the design of the guns for wing-mounting and remote control, larger drums were introduced as it would not be possible to exchange magazines in flight. For the FF series drum sizes of 45, 60, 75 and 100 rounds were available, but most users chose the 60-round drum.
The 1930s were a period of global re-armament, a number of foreign firms took licenses for the Oerlikon family of aircraft cannon. In France, Hispano-Suiza manufactured development of the FFS as the Hispano-Suiza HS.7 and Hispano-Suiza HS.9, for installation between the cylinder banks of its V-12 engines. In Germany, Ikaria further developed the FF gun as firing 20x80RB ammunition, and the Imperial Japanese Navy, after evaluating all three guns, ordered developments of the FF and FFL as the Type 99-1 and Type 99-2. The incorporation of the improvements of the FFS in a new anti-aircraft gun produced, in 1938, the Oerlikon SS. Oerlikon realized further improvements in rate of fire on the 1SS of 1942, the 2SS of 1945 which achieved 650 rpm. However, it was the original SS gun, adopted as anti-aircraft gun, being widely used by Allied navies during World War II; this gun used a 400-grain charge of IMR 4831 smokeless powder to propel a 2,000-grain projectile at 2,800 feet per second. The Oerlikon FF was installed as armament on some fighters of the 1930s, such as the Polish PZL P.24G.
Locally produced derivatives of the Oerlikon cannon were used much more extensively, on aircraft, on ships and on land. In the air, the Ikaria MG FF was used as armament on a number of German aircraft, of which the most famous is the Messerschmitt Bf 109; the Japanese Navy used their copy of the FF, designated the Type 99 Mark One cannon on a number of types including the Mitsubishi A6M Zero. In the war, they equipped fighters including the Zero with the Type 99 Mark Two, a version of the more powerful and faster-firing Oerlikon FFL; the French firm of Hispano-Suiza was a manufacturer of aircraft engines, it marketed the moteur-canon combination of its 12X and 12Y engines with a H. S.7 or H. S.9 cannon installed between the cylinder banks. The gun fired through the hollow propeller hub, this being elevated above the crankcase by the design of the gearing; such armament was installed on the Morane-Saulnier M. S.406 and some other types. Similar German installations of the MG FF were not successful.
The Oerlikon became best known in its naval applications. The Oerlikon was not looked upon favorably by the Royal Navy as a short-range anti-aircraft gun. All through 1937-1938 Lord Louis Mountbatten a Captain in the Royal Navy, waged a lone campaign within the Royal Navy to set up an unprejudiced trial for the Oerlikon 20 mm gun, but it was all in vain, it was not until the Commander-in-Chief of the Home Fleet, Admiral Sir Roger Backhouse, was appointed First Sea Lord tha
Guam is an unincorporated and organized territory of the United States in Micronesia in the western Pacific Ocean. It is the easternmost point and territory of the United States, along with the Northern Mariana Islands; the capital city of Guam is Hagåtña and the most populous city is Dededo. The inhabitants of Guam are called Guamanians, they are American citizens by birth. Indigenous Guamanians are the Chamorros, who are related to other Austronesian natives of Eastern Indonesia, the Philippines, Taiwan. Guam has been a member of the Pacific Community since 1983. In 2016, 162,742 people resided on Guam. Guam has a population density of 775 per square mile. In Oceania, it is the largest and southernmost of the Mariana Islands and the largest island in Micronesia. Among its municipalities, Mongmong-Toto-Maite has the highest population density at 3,691 per square mile, whereas Inarajan and Umatac have the lowest density at 119 per square mile; the highest point is Mount Lamlam at 1,332 feet above sea level.
Since the 1960s, the economy has been supported by two industries: tourism and the United States Armed Forces. The indigenous Chamorros settled the island 4,000 years ago. Portuguese explorer Ferdinand Magellan, while in the service of Spain, was the first European to visit the island, on March 6, 1521. Guam was colonized by Spain in 1668 with settlers, including Diego Luis de San Vitores, a Catholic Jesuit missionary. Between the 16th century and the 18th century, Guam was an important stopover for the Spanish Manila Galleons. During the Spanish–American War, the United States captured Guam on June 21, 1898. Under the Treaty of Paris, Spain ceded Guam to the United States on December 10, 1898. Guam is among the 17 non-self-governing territories listed by the United Nations. Before World War II, there were five American jurisdictions in the Pacific Ocean: Guam and Wake Island in Micronesia, American Samoa and Hawaii in Polynesia, the Philippines. On December 7, 1941, hours after the attack on Pearl Harbor, Guam was captured by the Japanese, who occupied the island for two and a half years.
During the occupation, Guamanians were subjected to beheadings, forced labor and torture. American forces recaptured the island on July 21, 1944. An unofficial but used territorial motto is "Where America's Day Begins", which refers to the island's close proximity to the international date line; the original inhabitants of Guam and the Northern Mariana Islands were the Chamorro people, who are believed to be descendants of Austronesian people originating from Southeast Asia as early as 2000 BC. The ancient Chamorro society had four classes: chamorri, matua and mana'chang; the matua were located in the coastal villages, which meant they had the best access to fishing grounds, whereas the mana'chang were located in the interior of the island. Matua and mana'chang communicated with each other, matua used achaot as intermediaries. There were "makåhna" or "kakahna", shamans with magical powers and "Suruhånu" or "Suruhåna" healers who use different kinds of plants and natural materials to make medicine.
Belief in spirits of ancient Chamorros called "Taotao mo'na" still persists as a remnant of pre-European culture. It is believed that "Suruhånu" or "Suruhåna" are the only ones who can safely harvest plants and other natural materials from their homes or "hålomtåno" without incurring the wrath of the "Taotao mo'na", their society was organized along matrilineal clans. Latte stones are stone pillars; the latte-stone was used as a foundation. Latte stones consist of a base shaped from limestone called the haligi and with a capstone, or tåsa, made either from a large brain coral or limestone, placed on top. A possible source for these stones, the Rota Latte Stone Quarry, was discovered in 1925 on Rota; the first European to travel to Guam was Portuguese navigator Ferdinand Magellan, sailing for the King of Spain, when he sighted the island on March 6, 1521, during his fleet's circumnavigation of the globe. When Magellan arrived on Guam, he was greeted by hundreds of small outrigger canoes that appeared to be flying over the water, due to their considerable speed.
These outrigger canoes were called Proas, resulted in Magellan naming Guam Islas de las Velas Latinas. Antonio Pigafetta said that the name was "Island of Sails", but he writes that the inhabitants "entered the ships and stole whatever they could lay their hands on", including "the small boat, fastened to the poop of the flagship." "Those people are poor, but ingenious and thievish, on account of which we called those three islands Islas de los Ladrones." Despite Magellan's visit, Guam was not claimed by Spain until January 26, 1565, by General Miguel López de Legazpi. From 1565 to 1815, Guam and the Northern Mariana Islands, the only Spanish outposts in the Pacific Ocean east of the Philippines, were an important resting stop for the Manila galleons, a fleet that covered the Pacific trade route between Acapulco and Manila. To protect these Pacific fleets, Spain built several defensive structures that still stand today, such as Fort Nuestra Señora de la Soledad in Umatac. Guam is the biggest single segment of Micronesia, the largest islands between the island of Kyushu, New Guinea, the Philippines, the Hawaiian Islands.
Spanish colonization commenced on June 15, 1
Enewetak Atoll is a large coral atoll of 40 islands in the Pacific Ocean and with its 664 people forms a legislative district of the Ralik Chain of the Marshall Islands. With a land area total less than 5.85 square kilometres, it is no higher than 5 meters and surrounds a deep central lagoon, 80 kilometres in circumference. It is 305 kilometres west from Bikini Atoll, it was held by the Japanese from 1914 until its capture by the United States in February of 1944, during World War II. Nuclear testing by the US totaling more than 30 megatons of TNT took place during the cold war; the Runit Dome is deteriorating and could be breached by a typhoon, though the sediments in the lagoon are more radioactive than those which are contained. The U. S. government referred to the atoll as "Eniwetok" until 1974, when it changed its official spelling to "Enewetak". Enewetak Atoll formed atop a seamount; the seamount was formed in the late Cretaceous. This seamount is now about 1,400 metres below sea level, it is made of basalt, its depth is due to a general subsidence of the entire region and not because of erosion.
Enewetak has a mean elevation above sea level of 3 metres. Humans have inhabited the atoll since about 1,000 B. C; the first European visitor to Enewetak, Spanish explorer Alvaro de Saavedra, arrived on 10 October 1529. He called the island "Los Jardines". In 1794 sailors aboard the British merchant sloop Walpole called the islands "Brown's Range", it was visited by about a dozen ships before the establishment of the German colony of the Marshall Islands in 1885. With the rest of the Marshalls, Enewetak was captured by the Imperial Japanese Navy in 1914 during World War I and mandated to the Empire of Japan by the League of Nations in 1920; the Japanese administered the island under the South Pacific Mandate, but left affairs in hands of traditional local leaders until the start of World War II. The atoll, together with other part of Marshall Islands located to the west of 164°E, was placed under the governance of Pohnpei district during the Japanese administration period, is different from rest of Marshall Islands.
In November 1942, the Japanese built an airfield on Engebi Island. As they used it only for refueling planes between Truk and islands to the east, no aviation personnel were stationed there and the island had only token defenses; when the Gilberts fell to the United States, the Imperial Japanese Army assigned defense of the atoll to the 1st Amphibious Brigade, formed from the 3rd Independent Garrison, stationed in Manchukuo. The 1st Amphibious Brigade arrived on January 4, 1944; some 2,586 of its 3,940 men were left to defend Eniwetok Atoll, supplemented by aviation personnel, civilian employees, laborers. However, they were unable to finish the fortifications. During the ensuing Battle of Eniwetok, the Americans captured Enewetak in a five-day amphibious operation. Fighting took place on Engebi Islet, site of the most important Japanese installation, although some combat occurred on the main islet of Enewetak itself and on Parry Island, where there was a Japanese seaplane base. Following its capture, the anchorage at Enewetak became a major forward base for the U.
S. Navy; the daily average of ships present during the first half of July 1944 was 488. In 1950, John C. Woods, who executed the Nazi war criminals convicted at the Nuremberg Trials, was accidentally electrocuted here. After the end of World War II, Enewetak came under the control of the United States as part of the Trust Territory of the Pacific Islands until the independence of the Marshall Islands in 1986. During its tenure, the United States evacuated the local residents many times involuntarily; the atoll was used for nuclear testing as part of the Pacific Proving Grounds. Before testing commenced, the U. S. exhumed the bodies of United States servicemen killed in the Battle of Enewetak and returned them to the United States to be re-buried by their families. Forty-three nuclear tests were fired at Enewetak from 1948 to 1958; the first hydrogen bomb test, code-named Ivy Mike, occurred in late 1952 as part of Operation Ivy. This test included B-17 Flying Fortress drones to fly through the radioactive cloud to test onboard samples.
B-17 mother ships controlled the drones while flying within visual distance of them. In all 16 to 20 B-17s took part in this operation, of which half were controlling aircraft and half were drones. To examine the explosion clouds of the nuclear bombs in 1957/58 several rockets were launched. One USAF airman was lost at sea during the tests. A radiological survey of Enewetak was conducted from 1972 to 1973. In 1977, the United States military began decontamination of other islands. During the three-year, US$100 million cleanup process, the military mixed more than 80,000 cubic metres of contaminated soil and debris from the islands with Portland cement and buried it in an atomic blast crater on the northern end of the atoll's Runit Island; the material was placed in the 9.1-metre deep, 110-metre wide crater created by the May 5, 1958, "Cactus" nuclear weapons test
Okinawa Prefecture is the southernmost prefecture of Japan. It encompasses two thirds of the Ryukyu Islands in a chain over 1,000 kilometres long; the Ryukyu Islands extend southwest from Kagoshima Prefecture in Kyushu to Taiwan. Naha, Okinawa's capital, is located in the southern part of Okinawa Island. Although Okinawa Prefecture comprises just 0.6 percent of Japan's total land mass, about 75 percent of all United States military personnel stationed in Japan are assigned to installations in the prefecture. About 26,000 U. S. troops are based in the prefecture. The oldest evidence of human existence on the Ryukyu islands is from the Stone Age and was discovered in Naha and Yaeyama; some human bone fragments from the Paleolithic era were unearthed from a site in Naha, but the artifact was lost in transportation before it was examined to be Paleolithic or not. Japanese Jōmon influences are dominant on the Okinawa Islands, although clay vessels on the Sakishima Islands have a commonality with those in Taiwan.
The first mention of the word Ryukyu was written in the Book of Sui. Okinawa was the Japanese word identifying the islands, first seen in the biography of Jianzhen, written in 779. Agricultural societies begun in the 8th century developed until the 12th century. Since the islands are located at the eastern perimeter of the East China Sea close to Japan and South-East Asia, the Ryukyu Kingdom became a prosperous trading nation. During this period, many Gusukus, similar to castles, were constructed; the Ryukyu Kingdom entered into the Imperial Chinese tributary system under the Ming dynasty beginning in the 15th century, which established economic relations between the two nations. In 1609, the Shimazu clan, which controlled the region, now Kagoshima Prefecture, invaded the Ryukyu Kingdom; the Ryukyu Kingdom was obliged to agree to form a suzerain-vassal relationship with the Satsuma and the Tokugawa shogunate, while maintaining its previous role within the Chinese tributary system. The Satsuma clan earned considerable profits from trade with China during a period in which foreign trade was restricted by the shogunate.
Although Satsuma maintained strong influence over the islands, the Ryukyu Kingdom maintained a considerable degree of domestic political freedom for over two hundred years. Four years after the 1868 Meiji Restoration, the Japanese government, through military incursions annexed the kingdom and renamed it Ryukyu han. At the time, the Qing Empire asserted a nominal suzerainty over the islands of the Ryukyu Kingdom, since the Ryūkyū Kingdom was a member state of the Chinese tributary system. Ryukyu han became Okinawa Prefecture of Japan in 1879 though all other hans had become prefectures of Japan in 1872. In 1912, Okinawans first obtained the right to vote for representatives to the National Diet, established in 1890. Near the end of World War II, in 1945, the US Army and Marine Corps invaded Okinawa with 185,000 troops. A third of the civilian population died; the dead, of all nationalities, are commemorated at the Cornerstone of Peace. After the end of World War II, the Ryukyu independence movement developed, while Okinawa was under United States Military Government of the Ryukyu Islands administration for 27 years.
During this "trusteeship rule", the United States established numerous military bases on the Ryukyu islands. During the Korean War, B-29 Superfortresses flew bombing missions over Korea from Kadena Air Base on Okinawa; the military buildup on the island during the Cold War increased a division between local inhabitants and the American military. Under the 1952 Treaty of Mutual Cooperation and Security between the United States and Japan, the United States Forces Japan have maintained a large military presence. Since 1960, the U. S. and Japan have maintained an agreement that allows the U. S. to secretly bring nuclear weapons into Japanese ports. The Japanese tended to oppose the introduction of nuclear arms into Japanese territory by the government's assertion of Japan's non-nuclear policy and a statement of the Three Non-Nuclear Principles. Most of the weapons were alleged to be stored in ammunition bunkers at Kadena Air Base. Between 1954 and 1972, 19 different types of nuclear weapons were deployed in Okinawa, but with fewer than around 1,000 warheads at any one time.
Between 1965 and 1972, Okinawa was a key staging point for the United States in its military operations directed towards North Vietnam. Along with Guam, it presented a geographically strategic launch pad for covert bombing missions over Cambodia and Laos. Anti-Vietnam War sentiment became linked politically to the movement for reversion of Okinawa to Japan. In 1965, the US military bases, earlier viewed as paternal post war protection, were seen as aggressive; the Vietnam War highlighted the differences between the United States and Okinawa, but showed a commonality between the islands and mainland Japan. As controversy grew regarding the alleged placement of nuclear weapons on Okinawa, fears intensified over the escalation of the Vietnam War. Okinawa was perceived, by some inside Japan, as a potential target for China, should the communist government feel threatened by the United States. American military secrecy blocked any local reporting on what was occurring at bases such as Kadena Air Base.
As information leaked out, images of air strikes were published, the local population began to fear the potential for retaliation. Political leaders such as Oda Makoto
3"/50 caliber gun
The 3″/50 caliber gun in United States naval gun terminology indicates the gun fired a projectile 3 inches in diameter, the barrel was 50 calibers long. Different guns of this caliber were used by the U. S. Navy and U. S. Coast Guard from 1890 through the 1990s on a variety of combatant and transport ship classes; the gun is still in use with the Spanish Navy on Serviola-class patrol boats. The US Navy's first 3″/50 caliber gun was an early model with a projectile velocity of 2,100 feet per second. Low-angle mountings for this gun had a range of 7000 yards at the maximum elevation of 15 degrees; the gun entered service around 1900 with the Bainbridge-class destroyers, was fitted to Connecticut-class battleships. By World War II these guns were found only on a few Coast Guard cutters and Defensively Equipped Merchant Ships. Low-angle 3″/50 caliber guns were mounted on ships built from the early 1900s through the early 1920s and were carried by submarines and merchant ships during the Second World War.
These guns fired the same 2,700 feet per second ammunition used by the following dual-purpose Marks, but with range limited by the maximum elevation of the mounting. These were built-up guns with a tube, partial-length jacket and vertical sliding breech block. Dual-purpose 3″/50 caliber guns first entered service in 1915 as a refit to USS Texas, were subsequently mounted on many types of ships as the need for anti-aircraft protection was recognized. During World War II, they were the primary gun armament on destroyer escorts, patrol frigates, submarine chasers, some fleet submarines, other auxiliary vessels, were used as a secondary dual-purpose battery on some other types of ships, including some older battleships, they replaced the original low-angle 4"/50 caliber guns on "flush-deck" Wickes and Clemson-class destroyers to provide better anti-aircraft protection. The gun was used on specialist destroyer conversions; these dual-purpose guns were "quick-firing", meaning that they used fixed ammunition, with powder case and projectile permanently attached, handled as a single unit weighing 34 pounds.
The shells alone weighed about 13 pounds including an explosive bursting charge of 0.81 pounds for anti-aircraft rounds or 1.27 pounds for High Capacity rounds, the remainder of the weight being the steel casing. Maximum range was 14,600 yards at 45 degrees elevation and ceiling was 29,800 feet at 85 degrees elevation. Useful life expectancy was 4300 effective full charges per barrel; the 3"/50 caliber gun Marks 17 and 18 was first used as a submarine deck gun on R-class submarines launched in 1918-1919. At the time it was an improvement on the earlier 3"/23 caliber gun. After using larger guns on many other submarines, the 3"/50 caliber gun Mark 21 was specified as the standard deck gun on the Porpoise- through Gato-class submarines launched in 1935-1942; the small gun was chosen to remove the temptation to engage enemy escort vessels on the surface. The gun was mounted aft of the conning tower to reduce submerged drag, but early in World War II it was shifted to a forward position at the commanding officer's option.
Wartime experience showed. This need was met by transferring 4"/50 caliber guns from S-class submarines as they were shifted from combat to training roles beginning in late 1942; the 5"/25 caliber gun removed from battleships sunk or damaged in the attack on Pearl Harbor and manufactured in a submarine version, became standard. When multiple hits from Oerlikon 20 mm cannon and Bofors 40 mm guns were unable to prevent kamikaze strikes during the final year of the second world war. Post-war experimentation with an extended range variant was abandoned as shipboard surface-to-air missiles were developed; the United States Navy considered contemporary 5"/38 caliber guns and 5″/54 caliber guns more effective against surface targets. The 3″/50 caliber gun was a semiautomatic anti-aircraft weapon with a power driven automatic loader; these monobloc 3 ″ guns were fitted to both twin mountings. The single was to be exchanged for a twin 40 mm antiaircraft gun mount and the twin for a quadruple 40 mm mount.
This was performed on Essex-class aircraft carriers, Allen M. Sumner and Gearing-class destroyers and other ships circa 1946-50. Although intended as a one-for-one replacement for the 40 mm mounts, the final version of the new 3-inch mounts was heavier than expected, on most ships the mounts could be replaced only on a two-for-three basis; the mounts were of open-base-ring type. The right and left gun assemblies were identical in the twin mounts; the mounts used a common power drive that could train at a rate of 30 degree/second and elevate from 15 degrees to 85 degrees at a rate of 24 degree/second. The cannon was fed automatically from an on-mount magazine, replenished during action by two loaders on each side of the cannon. With proximity fuze and fire-control radar, a twin 3″/50 mount firing 50 rounds per minute per