- published: 10 May 2013
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A trench is a type of excavation or depression in the ground. Trenches are generally defined by being deeper than they are wide (as opposed to a wider gully or ditch), and by being narrow compared to their length (as opposed to a simple hole).
Trench shoring is often used in trenchworks to protect workers and stabilize embankments.
Some trenches are created as a result of erosion by rivers (which may have long since fallen dry), others are created by geological movement of tectonic plates, such as rift valleys or more commonly oceanic trenches. Some oceanic trenches include the Mariana Trench and the Challenger Deep. The latter form is relatively deep (ca. 10 km), linear and narrow, and is formed by plate subduction when plates converge.
In the civil engineering field of construction or maintenance of infrastructure, trenches play a major role. They may be created to search for pipes and other infrastructure that is known to be underground in the general area, but whose exact location has been lost ('search trench' or 'search slit'). They are also used to underground easily damaged and obstructive infrastructure or utilities (such as gas mains, water mains or telephone lines). A similar use for higher bulk would be in pipeline transport. Finally, trenches may be created as the first step of creating a foundation wall.
World War I (WWI), which was predominantly called the World War or the Great War from its occurrence until 1939 (World War II), and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918. It involved all the world's great powers, which were assembled in two opposing alliances: the Allies (based on the Triple Entente of the United Kingdom, France and Russia) and the Central Powers (originally centred around the Triple Alliance of Germany, Austria-Hungary and Italy; but, as Austria–Hungary had taken the offensive against the agreement, Italy did not enter into the war). These alliances both reorganised (Italy fought for the Allies), and expanded as more nations entered the war. Ultimately more than 70 million military personnel, including 60 million Europeans, were mobilised in one of the largest wars in history. More than 9 million combatants were killed, largely because of enormous increases in lethality of weapons, thanks to new technology, without corresponding improvements in protection or mobility. It was the sixth-deadliest conflict in world history, subsequently paving the way for various political changes such as revolutions in the nations involved.