Ablockhouse is a smallfortification, usually consisting of one or more rooms withloopholes, allowing its defenders to fire in various directions.[1] It is usually an isolated fort in the form of a single building, serving as a defensive strong point against any enemy that does not possesssiege equipment or, in modern times,artillery,air force orcruise missiles. A fortification intended to resist these weapons is more likely to qualify as afortress or aredoubt, or in modern times, be an undergroundbunker. However, a blockhouse may also refer to a room within a larger fortification, usually abattery or redoubt.
The termblockhouse is of uncertain origin, perhaps related toMiddle Dutchblokhus and 18th-century Frenchblocus (blockade).[2]
Blockhouses existed in ancient Greece, for example the one nearMycenae.[3]
Early blockhouses were designed solely to protect a particular area by the use of artillery, and they had accommodation only for the short-term use of the garrison. The first known example is theCow Tower, Norwich, built in 1398, which was of brick and had three storeys with the upper storeys pierced for six guns each.[4] The major period of construction was in themaritime defence programmes ofHenry VIII between 1539 and 1545.[5] They were built to protect important maritime approaches such as theThames Estuary, theSolent, andPlymouth. Often sited in pairs, the blockhouses were not built to a common design, but usually consisted of a stone tower andbastion or gun platform, which could be semi-circular, rectangular or irregular in shape.[6] The last blockhouse of this type wasCromwell's Castle, built inScilly in 1651.
Blockhouses were an ubiquitous feature inMalta's coastal fortifications built in the 18th century by theOrder of St. John. Between 1714 and 1716, dozens ofbatteries andredoubts were built around the coasts of the Maltese Islands, while a few others were built in the subsequent decades. Almost every battery and redoubt had a blockhouse, which served as gun crew accommodation and a place to store munitions.[7]
Many of the batteries consisted of a semi-circular or polygonal gun platform, with one or two blockhouses at the rear. The blockhouses usually had musketry loopholes, and in some cases were linked together byredans. Surviving batteries includeMistra Battery andFerretti Battery, which both have two blockhouses, andSaint Mary's Battery andSaint Anthony's Battery, which have a single blockhouse.
Many of the redoubts consisted of a pentagonal platform with a rectangular blockhouse at the rear, although a few had semi-circular or rectangular platforms. Surviving redoubts with blockhouses includeBaħar iċ-Ċagħaq Redoubt andBriconet Redoubt, both of which have a pentagonal plan. A few of the redoubts consisted of a single tower-like blockhouse without a platform, and were known astour-reduits. Of the fourtour-reduits that were built, only theVendôme Tower survives today.[8]
Originally blockhouses were often constructed as part of a large plan, to "block" access to vital points in the scheme. But from theAge of Exploration to the nineteenth century standard patterns of blockhouses were constructed for defence in frontier areas, particularlySouth Africa,New Zealand,Canada,[9] and theUnited States.[10][11] Blockhouses may be made ofmasonry where available, but were commonly made from very heavytimbers, sometimes evenlogs arranged in the manner of alog cabin. They were usually two or even threefloors, with all storeys being provided withembrasures or loopholes, and the uppermost storey would be roofed. If the structure was of timber, usually the upper storey would project outward from the lower so the upper storey defenders could fire on enemies attacking the lower storey, or perhaps pour water on any fires. When the structure had only one storey, its loopholes were often placed close to the ceiling, with a bench lining the walls inside for defenders to stand on, so that attackers could not easily reach the loopholes.
Blockhouses were normally entered via a sturdy, barred door at ground level. Most blockhouses were roughly square inplan, but some of the more elaborate ones werehexagonal oroctagonal, to provide better all-around fire. In some cases, blockhouses became the basis for complete forts, by building apalisade with the blockhouse at one corner, and possibly a second tower at the opposite corner. Many historical stone blockhouses have survived, and a few timber ones have been restored at historical sites. In New Zealand, theCameron Blockhouse, nearWhanganui, is one of the few blockhouses to survive from theNew Zealand Wars.
During theSecond Boer War the British forces built a large number of fortifications inSouth Africa. Around 441 were solid masonry blockhouses,[12] many of which stand today. Different designs were used in the construction of these blockhouses, but most were either two or three story structures built using locally quarried stone.
However the vast scale of British strategy led the British to develop cheaper, double-skinned corrugated iron structures.[13] These could be prefabricated, delivered to site by armoured train, and then have locally sourced rocks or rubble packed inside the double skin to provide improved protection.
A circular design developed by Major Rice in February 1901 had good all round visibility, and the lack of corners did away with the need for a substructure.[14] Failure due to wood rot and splintering when hit by bullets or shrapnel were eliminated. The steel door to the blockhouse was sheltered by another piece of corrugated iron. The Major Rice blockhouse could be erected in six hours by six trained men. With the change from square gabled roofs to a circular design, they were given the nickname "Pepperpot blockhouse".[13] With mass production the cost to build a blockhouse dropped down to £16, compared to several hundred pounds for masonry ones.
These blockhouses played a vital role in the protection of the railway lines and bridges that were key to the British military supply lines.[12]
DuringWorld War I andWorld War II, many types of blockhouses were built, when time allowed usually constructed ofreinforced concrete. The major difference between a modern blockhouse and abunker is that a bunker is constructed mostly below ground level while a blockhouse is constructed mostly above ground level.[15]
Some blockhouses like those constructed in England in 1940 were builtin anticipation of a German invasion; they were oftenhexagonal in shape and were called "pillboxes". About 28,000pillboxes and other hardened field fortifications were constructed, of which about 6,500 still survive.[16]
TheAdmiralty Citadel in London is one of the sturdiest above-ground structures built during World War II. It was constructed in 1940–1941 as a bomb-proof operations centre for theAdmiralty, with foundations nine metres deep and a concrete roof six metres thick. It too was intended to serve as a strongpoint in defending against the feared invasion.
In Berlin and other cities duringWorld War II some massive blockhouses were built as air-raid shelters andanti-aircraft artillery platforms. They were calledHochbunker (literally, "high bunkers"; better translated as "above ground bunkers", to distinguish them from underground air raid shelters) and those that functioned as anti-aircraft artillery platforms were also calledFlak towers. Some were over six stories high; several survive because of the high cost of demolition. TheHochbunker Pallasstraße [de] in Berlin-Schöneberg has a post-war block of flats built over it. During theCold War the shelter was in use as a NATO foodstore.[citation needed]
In theguerrilla phase of the Irish Civil War (1922–1923), a network of blockhouses was constructed to protect the railways from guerrilla attacks.[citation needed]
Blockhouses and coordinated road systems were used in theencirclement campaigns ofChiang Kai-shek against theChinese Communist Party.[17]
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