Barbed wire, also known as barb wire (and frequently in dialect form spelled bob or bobbed), is a type of fencing wire constructed with sharp edges or points arranged at intervals along the strand(s). It is used to construct inexpensive fences and is used atop walls surrounding secured property. It is also a major feature of the fortifications in trench warfare (as a wire obstacle).
A person or animal trying to pass through or over barbed wire will suffer discomfort and possibly injury. Barbed wire fencing requires only fence posts, wire and fixing devices such as staples. It is simple to construct and quick to erect by an unskilled person.
Barbed wire was the first wire technology capable of restraining cattle. Wire fences were cheaper to erect than their alternatives and when they became widely available in the United States in the late 19th century they made it affordable to fence much larger areas than before. They made intensive animal husbandry practical on a much larger scale.
Waterman, Illinois farmer Henry Rose developed a fence consisting of a simple wooden strip with attached projecting wire points designed to dissuade encroaching livestock. He patented his design in May, 1873 (no. 138,763) and exhibited it at the DeKalb County Fair that summer. This prompted DeKalb area residents Isaac Ellwood, Joseph Glidden and Jacob Haish to work on improving the concept. Ellwood patented a type of barbed wire in February, 1874 (no. 147,756), but soon concluded that Glidden's design was superior to his own.
Glidden is purported to have made his early barbs with a modified coffee mill. He spaced the hand-made barbs on one strand of wire, which was then twisted together with another strand of wire to hold the barbs in place. Glidden was issued patent no. 157,124 in November, 1874. Meanwhile Isaac Ellwood had 874 and together they formed the Barb Fence Company in DeKalb. The business was quickly successful with production rising from in 1874 to nearly 3 million lbs in 1876. Jacob Haish also founded a successful business based on his own patents. In 1876 Glidden sold his remaining patent rights to the Washburn and Moen Manufacturing Company of Worcester, Massachusetts, which then joined with Ellwood to expand the business further.
This led to disputes known as the range wars between free-range ranchers and farmers in the late 19th century. These were similar to the disputes which resulted from enclosure laws in England in the early 18th century. These disputes were decisively settled in favor of the farmers, and heavy penalties were instituted for cutting a barbed wire fence. Within 25 years, nearly all of the open range had been fenced in under private ownership. For this reason, some historians have dated the end of the Old West era of American history to the invention and subsequent proliferation of barbed wire.
Barbed wire fences remain the standard fencing technology for enclosing cattle in most regions of the US, but not all countries. The wire is aligned under tension between heavy, braced, fence posts (strainer posts) and then held at the correct height by being attached to wooden posts and battens, or steel star posts. The gaps between star posts vary depending on terrain. On short fences in hilly country they may be placed every , while in flat terrain with long spans and relatively few stock they may be spaced up to 30 to . Wooden posts are normally spaced at 2 rods (10 m) in any case with 4 or 5 battens in between. Many farmers place posts 2 meters apart as battens can bend causing wires to close in on one another.
Barbed wire for agricultural fencing is typically available in two varieties—"soft" or mild-steel wire and "high-tensile". Both types are galvanized for longevity. High-tensile wire is made with thinner but higher-strength steel. Its greater strength make fences longer lasting because cattle cannot stretch and loosen it. It copes with the expansions and contraction caused by heat and animal pressure by stretching and relaxing within wider elastic limits. It also supports longer spans, but because of its "springy" nature it is hard to handle and somewhat dangerous for inexperienced fencers. Soft wire is much easier to work but is less durable and only suitable for short spans such as repairs and gates, where it is less likely to tangle.
In high soil-fertility areas where dairy cattle are used in great numbers 5- or 7-wire fences are common as the main boundary and internal dividing fences. On sheep farms 7-wire fences are common with the second (from bottom) to fifth wire being plain wire. In New Zealand wire fences must provide passage for dogs since they are the main means of controlling and driving animals on farms.
As with any fence, barbed wire fences require gates to allow the passage of persons, vehicles and farm implements. Gates vary in width from to allow the passage of vehicles and tractors, to on farm land to pass combines and swathers.
Gates for cattle tend to have 4 wires when along a three wire fence, as cattle tend to put more stress on gates, particularly on corner gates. The fence on each side of the gated ends with two corner posts braced or unbraced depending on the size of the post. An unpounded post (often an old broken post) is held to one corner post with wire rings which act as hinges. On the other end a full length post, the tractor post, is placed with the pointed end upwards with a ring on the bottom stapled to the other corner post, the latch post, and on top a ring is stapled to the tractor post, the post is tied with a Stockgrower's Lash or one of numerous other opening bindings. Wires are then tied around the post at one end then run to the other end where they are stretched by hand or with a stretcher, before posts are stapled on every , often this type of gate is called a Portagee Fence or a Portagee Gate in various ranching communities of coastal Central California.
Most gates can be opened by push post. The chain is then wrapped around the tractor post and pulled onto the nail, stronger people can pull the gate tighter but anyone can jar off the chain to open the gate.
Most barbed wire fences, while sufficient to discourage cattle, are passable by humans who can simply climb over the fence, or through the fence by stretching the gaps between the wires using non-barbed sections of the wire as hand holds. To prevent humans crossing, many prisons and other high-security installations construct fences with razor wire, a variant which instead of occasional barbs features near-continuous cutting surfaces sufficient to injure unprotected persons who climb on it. A commonly seen alternative is the placement of a few strands of barbed wire at the top of a chain link fence. The limited mobility of someone climbing a fence makes passing conventional barbed wire more difficult. On some chain link fences these strands are attached to a bracket tilted 45 degrees towards the intruder, increasing the difficulty.
Barbed wire began to be widely used as an implement of war during World War I. Wire was placed either to impede or halt the passage of soldiers, or to channel them into narrow defiles in which small arms, particularly machine guns, and indirect fire could be used with greater effect as they attempted to pass. Artillery bombardments on the Western Front became increasingly aimed at cutting the barbed wire that was a major component of trench warfare, particularly once new "wire-cutting" fuses were introduced midway through the war. As the war progressed the wire was used in shorter lengths that were easier to transport and more difficult to cut with artillery. Other inventions were also a result of the war, such as the screw-picket, which enabled construction of wire obstacles to be done at night in No Man's Land without the necessity of hammering stakes into the ground and drawing attention from the enemy.
During the Soviet-Afghan War, the accommodation of Afghan refugees into Pakistan was controlled in Pakistan's largest province, Balochistan, under General Rahimuddin Khan, by making the refugees stay for controlled durations in barbed wire camps (see Controlling Soviet-Afghan War Refugees).
The frequent use of barbed wire on prison walls, around concentration camps, and the like, has made it symbolic of oppression and denial of freedom in general. For example, in Germany the totality of the complex German Democratic Republic border regime is commonly referred to with the short phrase "Mauer und Stacheldraht" (that is, "wall and barbed wire"). Recently England and France have begun restricting the use of barbed wire due to the risk of injury it poses to trespassers.
Movement against barbed wire can result in moderate to severe injuries to the skin and, depending on body area and barbed wire configuration, possibly to the underlying tissue. Humans can manage not to injure themselves excessively when dealing with barbed wire as long as they are cautious. Restriction of movement, appropriate clothing, and slowing movement when close to barbed wire aid in reducing injury.
Injuries caused by barbed wire are typically seen in horses, bats or birds. Horses panic easily, and once caught in barbed wire, large patches of skin may be torn off. For this reason barbed wire was the single most important factor in rendering the U.S. Cavalry ineffective and led to the Cavalry's eventual dismantling. At best, such injuries may heal, but they may cause disability or death (particularly due to secondary infection). Birds or bats may not be able to perceive thin strands of barbed wire and suffer injuries. For this reason horse fences may have rubber bands nailed parallel to the wires. More than 60 different species of wildlife have been reported in Australia as victims of entanglement on barbed wire fences, and the wildlife friendly fencing project is beginning to address this problem. The project is funded mainly by the World Wide Fund for Nature. Grazing animals with slow movements which will back off at the first notion of pain — sheep, cows — will not generally suffer the severe injuries often seen in other animals.
Barbed wire has been reported as a tool for human torture.
The most important and most time-consuming part of a barbed wire fence is constructing the corner post and the bracing assembly. A barbed wire fence is under tremendous tension, often up to half a ton, and so the corner post's sole function is to resist the tension of the fence spans connected to it. The bracing keeps the corner post vertical and prevents slack from developing in the fence.
Brace posts are placed in-line about from the corner post. A horizontal compression brace connects the top of the two posts, and a diagonal wire connects the top of the brace post to the bottom of the corner post. This diagonal wire prevents the brace post from leaning, which in turn allows the horizontal brace to prevent the corner post from leaning into the brace post. A second set of brace posts (forming a double brace) is used whenever the barbed wire span exceeds 200 feet (60 m). If an 8" post is * feet in length is driven four feet into the ground the brace post assembly can be omitted.
When the barbed wire span exceeds 650 ft (200 m), a braced line assembly is added in-line. This has the function of a corner post and brace assembly but handles tension from opposite sides. It uses diagonal brace wire that connects the tops to the bottoms of all adjacent posts.
Line posts are installed along the span of the fence at intervals of 8 to 50 ft (2.5 m to 15 m). An interval of 16 ft (5 m) is most common. Heavy livestock and crowded pasture demands the smaller spacing. The sole function of a line post is not to take up slack but to keep the barbed wire strands spaced equally and off the ground.
Once these posts and bracing have been erected, the wire is wrapped around one corner post, held with a hitch (a timber hitch works well for this) often using a staple to hold the height and then reeled out along the span of the fence replacing the role every 400 m . It is then wrapped around the opposite corner post, pulled tightly with wire stretchers, and sometimes nailed with more fence staples, although this may make readjustment of tension or replacement of the wire more difficult. Then it is attached to all of the line posts with fencing staples driven in partially to allow stretching of the wire.
It is installed from the top down.
There are several ways to anchor the wire to a corner post:
Barbed wire for agriculture use is typically double-strand 12½-gauge, zinc-coated (galvanized) steel and comes in rolls of 1320 ft (402 m) length. Barbed wire is usually placed on the inner (pasture) side of the posts. Where a fence runs between two pastures livestock could be with the wire on the outside or on both sides of the fence.
Galvanized wire is classified into three categories; Classes I, II, and III. Class I has the thinnest coating and the shortest life expectancy. A wire with Class I coating will start showing general rusting in 8 to 10 years, while the same wire with Class III coating will show rust in 15 to 20 years. Aluminum-coated wire is occasionally used, and yields a longer life.
Corner posts are 6 to 8 inches (15 to 20 cm) in diameter or larger, and a minimum in length may consist of treated wood or from durable on-site trees such as osage orange, black locust, red cedar, or red mulberry, also railroad ties, telephone, and power poles are salvaged to be used as corner posts(poles and railroad ties were often treated with chemicals determined to be an environmental hazard and cannot be reused in some jurisdictions). In Canada spruce posts are sold for this purpose. Posts are driven at least and may be anchored in a concrete base 20 inches (50 cm) square and 42 inches (105 cm) deep. Brace posts are a minimum 4 inches (10 cm) in diameter and are anchored in a concrete base 20 inches (50 cm) square and 24 inches (60 cm) deep. Iron posts, if used, are a minimum 2½ inch (64 mm) in diameter. Bracing wire is typically smooth 9-gauge. Line posts are set to a depth of about 30 inches (75 cm). The main advantage of steel posts is that they can be driven with a post moll or a cylindrical tube closed at one end with plate steel for weight, and pulled out by hand as opposed to wooden posts which must be pounded with a hydraulic pounder and often pulled with a front end loader. Conversely steel posts are not as stiff as wood and wires are fastened with slips along fixed teeth which means variations in driving height effect wire spacing.
During the First World War, screw pickets were used for the installation of wire obstacles; these were metal rods with eyelets for holding strands of wire, and a corkscrew-like end that could literally be screwed into the ground rather than hammered, so that wiring parties could work at night near enemy soldiers and not reveal their position by the sound of hammers.
Patents – (about 570 were issued):