The City Municipality of Bremen is a Hanseatic city in northwestern Germany, which belongs to the Free Hanseatic City of Bremen, a federal state of Germany. As a commercial and industrial city with a major port on the River Weser, Bremen is part of the Bremen/Oldenburg Metropolitan Region, with 2.5 million people. Bremen is eleventh in Germany. Bremen is a major economic hub in the northern regions of Germany. Bremen is home to dozens of historical galleries and museums, ranging from historical sculptures to major art museums, such as the Übersee-Museum Bremen. Bremen has a reputation as a working-class city. Bremen is home to a large number of manufacturing centers. Companies headquartered in Bremen include Vector Foiltec. Four-time German football champions Werder Bremen are based in the city. Bremen is some 60 km south of the mouth of the Weser on the North Sea. Bremen and Bremerhaven together comprise the state of the Free Hanseatic City of Bremen; the marshes and moraines near Bremen have been settled since about 12,000 BC.
Burial places and settlements in Bremen-Mahndorf and Bremen-Osterholz date back to the 7th century AD. Since the Renaissance, some scientists have believed that the entry Fabiranum or Phabiranon in Ptolemy's Fourth Map of Europe, written in AD 150, refers to Bremen, but Ptolemy gives geographic coordinates, these refer to a site northeast of the mouth of the river Visurgis. In Ptolemy's time the Chauci lived in the area now called Lower Saxony. By the end of the 3rd century, they had merged with the Saxons. During the Saxon Wars the Saxons, led by Widukind, fought against the West Germanic Franks, the founders of the Carolingian Empire, lost the war. Charlemagne, the King of the Franks, made a new law, the Lex Saxonum, which forbid the Saxons worshipping Odin. In 787 Willehad of Bremen became the first Bishop of Bremen. In 848 the archdiocese of Hamburg merged with the diocese of Bremen to become Hamburg-Bremen Archdiocese, with its seat in Bremen, in the following centuries the archbishops of Hamburg-Bremen were the driving force behind the Christianisation of Northern Germany.
In 888, at the behest of Archbishop Rimbert, Kaiser Arnulf of Carinthia, the Carolingian King of East Francia, granted Bremen the rights to hold its own markets, mint its own coins and make its own customs laws. The city's first stone walls were built in 1032. Around that time trade with Norway and the northern Netherlands began to grow, thus increasing the importance of the city. In 1186 the Bremian Prince-Archbishop Hartwig of Uthlede and his bailiff in Bremen confirmed – without waiving the prince-archbishop's overlordship over the city – the Gelnhausen Privilege, by which Frederick I Barbarossa granted the city considerable privileges; the city was recognised as a political entity with its own laws. Property within the municipal boundaries could not be subjected to feudal overlordship. Property was to be inherited without feudal claims for reversion to its original owner; this privilege laid the foundation for Bremen's status of imperial immediacy. But in reality Bremen did not have complete independence from the Prince-Archbishops: there was no freedom of religion, burghers still had to pay taxes to the Prince-Archbishops.
Bremen played a double role: it participated in the Diets of the neighbouring Prince-Archbishopric of Bremen as part of the Bremian Estates and paid its share of taxes, at least when it had consented to this levy. Since the city was the major taxpayer, its consent was sought. In this way the city wielded fiscal and political power within the Prince-Archbishopric, while not allowing the Prince-Archbishopric to rule in the city against its consent. In 1260 Bremen joined the Hanseatic League. In 1350, the number of inhabitants reached 20,000. Around this time the Hansekogge became a unique product of Bremen. In 1362, representatives of Bremen rendered homage to Albert II, Prince-Archbishop of Bremen in Langwedel. In return, Albert confirmed the city's privileges and brokered a peace between the city and Gerhard III, Count of Hoya, who since 1358 had held some burghers of Bremen in captivity; the city had to bail them out. In 1365 an extra tax, levied to finance the ransom, caused an uprising among the burghers and artisans, put down by the city council after much bloodshed.
In 1366, Albert II tried to take advantage of the dispute between Bremen's city council and the guilds, whose members had expelled some city councillors from the city. When these councillors appealed to Albert II for help, many artisans and burghers regarded this as a treasonous act, fearing that this appeal to the prince would only provoke him to abolish the autonomy of the city; the fortified city maintained its own guards, not allowing soldiers of the Prince-Archbishop to enter it. The city reserved an extra narrow gate, the so-called Bishop's Needle, for all clergy, including the Prince-Archbishop; the narrowness of the gate made it physically impossible. On the night of 29 May 1366, Albert's troops, helped by some burghers, invaded the city. Afterward, the city had to a
The kilometre, or kilometer is a unit of length in the metric system, equal to one thousand metres. It is now the measurement unit used for expressing distances between geographical places on land in most of the world. K is used in some English-speaking countries as an alternative for the word kilometre in colloquial writing and speech. A slang term for the kilometre in the US and UK military is klick. There are two common pronunciations for the word; the former follows a pattern in English whereby metric units are pronounced with the stress on the first syllable and the pronunciation of the actual base unit does not change irrespective of the prefix. It is preferred by the British Broadcasting Corporation and the Australian Broadcasting Corporation. Many scientists and other users in countries where the metric system is not used, use the pronunciation with stress on the second syllable; the latter pronunciation follows the stress pattern used for the names of measuring instruments. The problem with this reasoning, however, is that the word meter in those usages refers to a measuring device, not a unit of length.
The contrast is more obvious in countries using the British rather than American spelling of the word metre. When Australia introduced the metric system in 1975, the first pronunciation was declared official by the government's Metric Conversion Board. However, the Australian prime minister at the time, Gough Whitlam, insisted that the second pronunciation was the correct one because of the Greek origins of the two parts of the word. By the 8 May 1790 decree, the Constituent assembly ordered the French Academy of Sciences to develop a new measurement system. In August 1793, the French National Convention decreed the metre as the sole length measurement system in the French Republic; the first name of the kilometre was "Millaire". Although the metre was formally defined in 1799, the myriametre was preferred to the "kilometre" for everyday use; the term "myriamètre" appeared a number of times in the text of Develey's book Physique d'Emile: ou, Principes de la science de la nature, while the term kilometre only appeared in an appendix.
French maps published in 1835 had scales showing myriametres and "lieues de Poste". The Dutch gave it the local name of the mijl, it was only in 1867 that the term "kilometer" became the only official unit of measure in the Netherlands to represent 1000 metres. Two German textbooks dated 1842 and 1848 give a snapshot of the use of the kilometre across Europe - the kilometre was in use in the Netherlands and in Italy and the myriametre was in use in France. In 1935, the International Committee for Weights and Measures abolished the prefix "myria-" and with it the "myriametre", leaving the kilometre as the recognised unit of length for measurements of that magnitude. In the United Kingdom, road signs show distances in miles and location marker posts that are used for reference purposes by road engineers and emergency services show distance references in unspecified units which are kilometre-based; the advent of the mobile phone has been instrumental in the British Department for Transport authorising the use of driver location signs to convey the distance reference information of location marker posts to road users should they need to contact the emergency services.
In the US, the National Highway System Designation Act of 1995 prohibits the use of federal-aid highway funds to convert existing signs or purchase new signs with metric units. The Executive Director of the US Federal Highway Administration, Jeffrey Paniati, wrote in a 2008 memo: "Section 205 of the National Highway System Designation Act of 1995 prohibited us from requiring any State DOT to use the metric system during project development activities. Although the State DOT's had the option of using metric measurements or dual units, all of them abandoned metric measurements and reverted to sole use of inch-pound values." The Manual on Uniform Traffic Control Devices since 2000 is published in both metric and American Customary Units. Some sporting disciplines feature 1000 m races in major events, but in other disciplines though world records are catalogued, the one kilometre event remains a minority event; the world records for various sporting disciplines are: Conversion of units, for comparison with other units of length Cubic metre Metric prefix Mileage Odometer Orders of magnitude Square kilometre Media related to Distance indicators at Wikimedia Commons
8.8 cm SK C/35 naval gun
The 8.8 cm SK C/35 was a German naval gun used in World War II. The 8.8 cm SK C/35 gun weighed 776 kilograms and had an overall length of 3.985 meters with a vertical sliding-block breech. The gun fired a 9.5 kg projectile 88 mm in diameter, the barrel is sometimes described as 45 caliber. A 2.82 kg propellent charge produced muzzle velocity of 700 m/s with nose-fuzed high explosive and high explosive incendiary projectiles. Useful life expectancy was 12,000 effective full charges per barrel. Ammunition was of a fixed type with a Complete Round Weight of 15 kg and a projectile length of around 355 mm; the gun was able to fire Armor Piercing - 10.2 kg High Explosive - 9 kg Illumination - 9.4 kg The High Explosive round has a muzzle velocity of 700 m/s This was the standard deck gun mounted forward of the conning tower in Type VII boats, although a few substituted a high-angle 8.8 cm SK C/30 naval gun for anti-aircraft defense. The SK C/35 was designed for the prototype VIIA boats of 1935 with a nominal ammunition allowance of 220 rounds.
During the early war years, these guns were used to encourage surrender of independently routed merchant ships or to sink ships damaged by torpedoes. Some of these guns were removed from U-boats for mounting aboard minesweepers and submarine chasers after unshielded deck guns proved impractical in action against Defensively Equipped Merchant Ships and escorted trade convoys. List of naval guns Blair, Clay. Hitler's U-Boat War: The Hunters 1939-1942. New York: Random House. ISBN 0-394-58839-8. Campbell, John. Naval Weapons of World War Two. London: Conway Maritime Press. ISBN 0-87021-459-4. Gander, Terry. Weapons of the Third Reich: An Encyclopedic Survey of All Small Arms and Special Weapons of the German Land Forces 1939–1945. New York: Doubleday. ISBN 0-385-15090-3. Hogg, Ian V.. German Artillery of World War Two. Mechanicsville, PA: Stackpole Books. ISBN 1-85367-480-X. Lenton, H. T.. German Warships of the Second World War. New York: Arco. ISBN 0-668-04037-8. Rolf, Rudi. Der Atlantikwall: Bauten der deutschen Küstenbefestigungen 1940-1945.
Osnabrück: Biblio. ISBN 3-7648-2469-7. Rolf, Rudi. A Dictionary on Modern Fortification: An Illustrated Lexicon on European Fortification in the Period 1800-1945. Middleburg, Netherlands: PRAK. SK C/35 at Navweaps.com
2 cm Flak 30/38/Flakvierling
The Flak 30 and improved Flak 38 were 20 mm anti-aircraft guns used by various German forces throughout World War II. It was not only the primary German light anti-aircraft gun, but by far the most numerously produced German artillery piece throughout the war, it was produced in a variety of models, notably the Flakvierling 38 which combined four Flak 38 autocannons onto a single carriage. The Germans fielded the unrelated early 2 cm Flak 28 just after World War I, but the Treaty of Versailles outlawed these weapons and they were sold to Switzerland; the original Flak 30 design was developed from the Solothurn ST-5 as a project for the Kriegsmarine, which produced the 20 mm C/30. The gun fired the "Long Solothurn", a 20 × 138 mm belted cartridge, developed for the ST-5 and was one of the most powerful 20 mm rounds in existence; the C/30, featuring a barrel length of 65 calibres, had a rate of about 120 rounds per minute. Disappointingly, it proved to have feeding problems and would jam, offset to some degree by its undersized 20 round-magazine which tended to make reloading a frequent necessity.
The C/30 became the primary shipborne light AA weapon and equipped a large variety of German ships. The MG C/30L variant was used experimentally as an aircraft weapon, notably on the Heinkel He 112, where its high power allowed it to penetrate armored cars and the light tanks of the era during the Spanish Civil War. Rheinmetall started an adaptation of the C/30 for Army use, producing the 2 cm Flak 30. Similar to the C/30, the main areas of development were the mount, compact. Set-up could be accomplished by dropping the gun to the ground off its two-wheeled carriage and levelling with hand cranks; the result was a triangular base. But the main problem with the design remained unsolved; the rate of fire of 120 RPM was not fast for a weapon of this calibre. Rheinmetall responded with the 2 cm Flak 38, otherwise similar but increased the rate of fire to 220 RPM and lowered overall weight to 420 kg; the Flak 38 was accepted as the standard Army gun in 1939, by the Kriegsmarine as the C/38. In order to provide airborne and mountain troops with AA capabilities, Mauser was contracted to produce a lighter version of the Flak 38, which they introduced as the 2 cm Gebirgsflak 38.
It featured a simplified mount using a tripod that raised the entire gun off the ground, which had the side benefit of allowing it to be set up on an uneven surface. These changes reduced the overall weight of the gun to a mere 276.0 kg. Production started in 1941 and entered service in 1942. A wide variety of 20x138B ammunition was manufactured to be used in 2 cm Flak weapons. Other kinds than in existence included a number of different AP types. A high-velocity PzGr 40 round with a tungsten carbide core in an aluminium body existed in 20x138B caliber; as the Flak 30 was entering service, the Luftwaffe and Heer branches of the Wehrmacht had doubts about its effectiveness, given the ever-increasing speeds of low-altitude fighter-bombers and attack aircraft. The Army in particular felt the proper solution was the introduction of the 37 mm caliber weapons they had been developing since the 1920s, which had a rate of fire about the same as the Flak 38, but fired a round with eight times the weight.
This not only made the rounds deadlier on impact, but their higher energy and ballistic coefficient allowed them to travel much longer distances, allowing the gun to engage targets at longer ranges. This meant; the 20 mm weapons had always had weak development perspectives being reconfigured or redesigned just enough to allow the weapons to find use. Indeed, it came as a surprise when Rheinmetall introduced the 2 cm Flakvierling 38, which improved the weapon just enough to make it competitive once again; the term Vierling translates to "quadruplet" and refers to the four 20 mm autocannon constituting the design. The Flakvierling weapon consisted of quad-mounted 2 cm Flak 38 AA guns with collapsing seats, folding handles, ammunition racks; the mount had a triangular base with a jack at each leg for levelling the gun. The tracker elevated the mount manually using two handwheels; when raised, the weapon measured 307 cm high. Each of the four mounted; this meant that a maximum combined rate of fire of 1,400 rounds per minute was reduced to 800 rounds per minute for combat use – which would still require that an emptied magazine be replaced every six seconds, on each of the four guns.
This is the attainable rate of fire. Automatic weapons are limited to 100 rounds per minute per barrel to give time for the heat to dissipate, although this can be exceeded for short periods if the firing window is brief; the gun was fired by a set of two pedals — each of which fired two diametrically opposite barrels — in either semi-automatic or automatic mode. The effective vertical range was 2,200 metres, it was used just as against ground targets as it was against low-flying aircraft. The Flakvierling four-autocannon anti-aircraft ordnance system, when not mounted into any self-propelled mount, was transported on a Sd. Ah. 52 trailer, could be towed behind a variety of half-tracks or trucks, such as the Opel Blitz and the armored Sd. Kfz. 251 and un
HMS Fortune (H70)
HMS Fortune was one of nine F-class destroyers built for the Royal Navy in the mid-1930s. Although she was assigned to the Home Fleet upon completion, the ship was detached to the Mediterranean Fleet to enforce the arms blockade imposed by Britain and France on both sides during the Spanish Civil War of 1936–39. Several weeks after the start of the Second World War in September 1939, Fortune helped to sink a German submarine; the ship escorted the larger ships of the fleet during the early stages of World War II and played a minor role in the Norwegian Campaign of 1940. Fortune was sent to Gibraltar in mid-1940 and formed part of Force H where she participated in the Battle of Dakar against the Vichy French; the ship escorted numerous convoys to Malta in 1940–41 until she was badly damaged by Italian bombers in mid-1941. After repairs were completed, Fortune was assigned to the Mediterranean Fleet before she was transferred to the Eastern Fleet in the Indian Ocean in early 1942; the ship screened an aircraft carrier during the Battle of Madagascar that year and was assigned to convoy escort duties for the rest of 1942 and early 1943.
She returned home in February to begin conversion into an escort destroyer. The ship was transferred to the Royal Canadian Navy when it was completed in mid-1943 and renamed HMCS Saskatchewan; the ship spent the next year escorting convoys in the North Atlantic before she was transferred to the English Channel to defend convoys during the Normandy landings in June 1944. Sasketchewan engaged some German patrol boats the following month and was damaged, she was sent to Canada for repairs and a general refit and did not return to the UK until January 1945. The ship resumed her former duties until the end of the war in May and ferried troops back to Canada for several months. Sasketchewan was judged surplus that year and was sold for scrap, in early 1946; the F-class ships were repeats of the preceding E class. They displaced 1,405 long tons at 1,940 long tons at deep load; the ships had an overall length of 329 feet, a beam of 33 feet 3 inches and a draught of 12 feet 6 inches. They were powered by two Brown-Curtis geared steam turbines, each driving one propeller shaft, using steam provided by three Admiralty three-drum boilers.
The turbines gave a maximum speed of 35.5 knots. Fortune exceeded her designed speed during her sea trials, she carried a maximum of 470 long tons of fuel oil that gave her a range of 6,350 nautical miles at 15 knots. The ships' complement was 145 ratings; the ships mounted four 4.7-inch Mark IX guns in single mounts in single mounts, designated'A','B','X', and'Y' in sequence from front to rear. For anti-aircraft defence, they had two quadruple Mark I mounts for the 0.5 inch Vickers Mark III machine gun. The F class was fitted with two above-water quadruple torpedo tube mounts for 21-inch torpedoes. One depth charge rack and two throwers were fitted. Fortune had her rear torpedo tubes replaced by a 12-pounder AA gun by April 1941. In February–May 1943, she was converted into an escort destroyer. A Type 286 short-range surface search radar was fitted and a Type 271 target indication radar was installed above the bridge, replacing the director-control tower and rangefinder; the ship received a HF/DF radio direction finder mounted on a pole mainmast.
Her short-range AA armament was augmented by four 20 mm Oerlikon guns and the.50-calibre machine guns were replaced by a pair of Oerlikons. A split Hedgehog anti-submarine spigot mortar was installed abreast'A' gun and stowage for a total of 70 depth charges meant that'Y' gun, the 12-pounder and her Two-Speed Destroyer Sweep minesweeping gear had to be removed to compensate for their weight. Fortune, the 23rd ship of that name in the Royal Navy, was laid down by John Brown & Company at their Clydebank shipyard on 27 July 1933, she was launched on 29 August 1934 and completed on 27 April 1935. The ship cost 247,564 pounds, excluding government-furnished equipment like the armament. Fortune was assigned to the 6th Destroyer Flotilla of the Home Fleet, but detached to the Mediterranean Fleet in 1937 to enforce the arms embargo imposed on both sides in the Spanish Civil War by the Non-Intervention Committee; the 6th DF was renumbered the 8th Destroyer Flotilla in April 1939, five months before the start of World War II.
After a pair of fishing trawlers were sunk by a submarine off the Hebrides after the start of World War II in September 1939, the 6th and 8th DFs were ordered to sweep the area on 19 September. The following day and three of her sister ships sank the German submarine U-27 and resumed their normal escort duties. In February 1940, she was one of the escorts for Convoy TC 3 carrying troops from Canada to the UK. In the following month, while escorting units of the Home Fleet north-west of the Shetlands on 20 March, she was credited with sinking U-44, although research suggests that the submarine was destroyed in a minefield, laid by other British destroyers on 13 March. During the Norwegian Campaign, Fortune played a minor role escorting the oiler RFA War Pindari to Namsos on 15 April. On 25 April, she ferried part of the 2nd Battalion, the South Wales Borderers to Lenvik. A few days the ship escorted the aircraft carriers Ark Royal and Glorious and the battleship Valiant off the coast of Norway.
In early May, she escorted two cruisers ferrying troops to occupy Iceland. In August, Fortune was transferred to the 4
U-boat is an anglicised version of the German word U-Boot, a shortening of Unterseeboot "underseaboat." While the German term refers to any submarine, the English one refers to military submarines operated by Germany in the First and Second World Wars. Although at times they were efficient fleet weapons against enemy naval warships, they were most used in an economic warfare role and enforcing a naval blockade against enemy shipping; the primary targets of the U-boat campaigns in both wars were the merchant convoys bringing supplies from Canada and other parts of the British Empire, from the United States to the United Kingdom and to the Soviet Union and the Allied territories in the Mediterranean. German submarines destroyed Brazilian merchant ships during World War II, causing Brazil to declare war on the Axis powers in 1944. Austro-Hungarian Navy submarines were known as U-boats; the first submarine built in Germany, the three-man Brandtaucher, sank to the bottom of Kiel harbor on 1 February 1851 during a test dive.
The inventor and engineer Wilhelm Bauer had designed this vessel in 1850, Schweffel & Howaldt constructed it in Kiel. Dredging operations in 1887 rediscovered Brandtaucher. There followed in 1890 the boats WW2, built to a Nordenfelt design. In 1903 the Friedrich Krupp Germaniawerft dockyard in Kiel completed the first functional German-built submarine, which Krupp sold to Russia during the Russo-Japanese War in April 1904; the SM U-1 was a redesigned Karp-class submarine and only one was built. The Imperial German Navy commissioned it on 14 December 1906, it had a double hull, a Körting kerosene engine, a single torpedo tube. The 50%-larger SM U-2 had two torpedo tubes; the U-19 class of 1912–13 saw the first diesel engine installed in a German navy boat. At the start of World War I in 1914, Germany had 48 submarines of 13 classes in service or under construction. During that war the Imperial German Navy used SM U-1 for training. Retired in 1919, it remains on display at the Deutsches Museum in Munich.
On 5 September 1914, HMS Pathfinder was sunk by SM U-21, the first ship to have been sunk by a submarine using a self-propelled torpedo. On 22 September, U-9 under the command of Otto Weddigen sank the obsolete British warships HMS Aboukir, HMS Cressy and HMS Hogue in a single hour. In the Gallipoli Campaign in early 1915 in the eastern Mediterranean, German U-boats, notably the U-21, prevented close support of allied troops by 18 pre-Dreadnought battleships by sinking two of them. For the first few months of the war, U-boat anticommerce actions observed the "prize rules" of the time, which governed the treatment of enemy civilian ships and their occupants. On 20 October 1914, SM U-17 sank the SS Glitra, off Norway. Surface commerce raiders were proving to be ineffective, on 4 February 1915, the Kaiser assented to the declaration of a war zone in the waters around the British Isles; this was cited as a retaliation for British minefields and shipping blockades. Under the instructions given to U-boat captains, they could sink merchant ships potentially neutral ones, without warning.
In February 1915, a submarine U-6 was rammed and both periscopes were destroyed off Beachy Head by the collier SS Thordis commanded by Captain John Bell RNR after firing a torpedo. On 7 May 1915, SM U-20 sank the liner RMS Lusitania; the sinking claimed 1,198 lives, 128 of them American civilians, the attack of this unarmed civilian ship shocked the Allies. According to the ship's manifest, Lusitania was carrying military cargo, though none of this information was relayed to the citizens of Britain and the United States who thought that the ship contained no ammunition or military weaponry whatsoever and it was an act of brutal murder. Munitions that it carried were thousands of crates full of ammunition for rifles, 3-inch artillery shells, various other standard ammunition used by infantry; the sinking of the Lusitania was used as propaganda against the German Empire and caused greater support for the war effort. A widespread reaction in the U. S was not seen until the sinking of the ferry SS Sussex.
The sinking occurred in 1915 and the United States entered the war in 1917. The initial U. S. response was to threaten to sever diplomatic ties, which persuaded the Germans to issue the Sussex pledge that reimposed restrictions on U-boat activity. The U. S. reiterated its objections to German submarine warfare whenever U. S. civilians died as a result of German attacks, which prompted the Germans to reapply prize rules. This, removed the effectiveness of the U-boat fleet, the Germans sought a decisive surface action, a strategy that culminated in the Battle of Jutland. Although the Germans claimed victory at Jutland, the British Grand Fleet remained in control at sea, it was necessary to return to effective anticommerce warfare by U-boats. Vice-Admiral Reinhard Scheer, Commander in Chief of the High Seas Fleet, pressed for all-out U-boat war, convinced that a high rate of shipping losses would force Britain to seek an early peace before the United States could react effectively; the renewed German campaign was effective, sinking 1.4 million tons of shipping between October 1916 and January 1917.
Despite this, the political situation demanded greater pressure, on 31 January 1917, Germany announced that its U-boats would engage in unrestricted submarine warfare beginning 1 February. On 17 March, German submarines sank three American merchant vessels, the U. S. declared wa
Anti-aircraft warfare or counter-air defence is defined by NATO as "all measures designed to nullify or reduce the effectiveness of hostile air action". They include surface based and air-based weapon systems, associated sensor systems and control arrangements and passive measures, it may be used to protect naval and air forces in any location. However, for most countries the main effort has tended to be'homeland defence'. NATO refers to airborne naval air defence as anti-aircraft warfare. Missile defence is an extension of air defence as are initiatives to adapt air defence to the task of intercepting any projectile in flight. In some countries, such as Britain and Germany during the Second World War, the Soviet Union, NATO, the United States, ground-based air defence and air defence aircraft have been under integrated command and control. However, while overall air defence may be for homeland defence including military facilities, forces in the field, wherever they are, invariably deploy their own air defence capability if there is an air threat.
A surface-based air defence capability can be deployed offensively to deny the use of airspace to an opponent. Until the 1950s, guns firing ballistic munitions ranging from 7.62 mm to 152.4 mm were the standard weapons. The term air defence was first used by Britain when Air Defence of Great Britain was created as a Royal Air Force command in 1925. However, arrangements in the UK were called'anti-aircraft', abbreviated as AA, a term that remained in general use into the 1950s. After the First World War it was sometimes prefixed by'Light' or'Heavy' to classify a type of gun or unit. Nicknames for anti-aircraft guns include AA, AAA or triple-A, an abbreviation of anti-aircraft artillery. NATO defines anti-aircraft warfare as "measures taken to defend a maritime force against attacks by airborne weapons launched from aircraft, ships and land-based sites". In some armies the term All-Arms Air Defence is used for air defence by nonspecialist troops. Other terms from the late 20th century include GBAD with related terms SHORAD and MANPADS.
Anti-aircraft missiles are variously called surface-to-air missile and pronounced "SAM" and Surface to Air Guided Weapon. Non-English terms for air defence include the German FlaK, whence English flak, the Russian term Protivovozdushnaya oborona, a literal translation of "anti-air defence", abbreviated as PVO. In Russian the AA systems are called zenitnye systems. In French, air defence is called DCA; the maximum distance at which a gun or missile can engage an aircraft is an important figure. However, many different definitions are used but unless the same definition is used, performance of different guns or missiles cannot be compared. For AA guns only the ascending part of the trajectory can be usefully used. One term is "ceiling", the maximum ceiling being the height a projectile would reach if fired vertically, not useful in itself as few AA guns are able to fire vertically, maximum fuse duration may be too short, but useful as a standard to compare different weapons; the British adopted "effective ceiling", meaning the altitude at which a gun could deliver a series of shells against a moving target.
By the late 1930s the British definition was "that height at which a directly approaching target at 400 mph can be engaged for 20 seconds before the gun reaches 70 degrees elevation". However, effective ceiling for heavy AA guns was affected by nonballistic factors: The maximum running time of the fuse, this set the maximum usable time of flight; the capability of fire control instruments to determine target height at long range. The precision of the cyclic rate of fire, the fuse length had to be calculated and set for where the target would be at the time of flight after firing, to do this meant knowing when the round would fire; the essence of air defence is to destroy them. The critical issue is to hit a target moving in three-dimensional space; this means that projectiles either have to be guided to hit the target, or aimed at the predicted position of the target at the time the projectile reaches it, taking into account speed and direction of both the target and the projectile. Throughout the 20th century, air defence was one of the fastest-evolving areas of military technology, responding to the evolution of aircraft and exploiting various enabling technologies radar, guided missiles and computing (initially electromechanical analogue computing from the 1930s on, as with equipment describ