These measures, usually comprising earthworks or dykes as well as ditches and impenetrable lines of hedging, for protecting towns and villages date mainly to the High and Late Middle Ages and consist, in some cases, of systems over a hundred kilometres long.
The construction of a landwehr was an effective way of protecting the population of a settlement or territory against attacks by neighbours or enemies in feuds or war, and also to mark out the legal limits of an area.
The only gaps in landwehr defences were on roads entering the area where, like the gates in a town wall, people and goods were checked as they passed through.
In addition to protecting travellers from ambushes, these landwehrs on either side of the route were mainly used to channel the flow of traffic and effectively prevent people bypassing or avoiding check points and customs posts.
Even in prehistoric and early historic times, people built defensive enclosures using branches and brambles for the protection of storage places (including caves), fortified residences, houses, estates and settlements from attack by predators or enemies.
Julius Caesar tells e.g. of thick Hagen which were laid out by the Nervii, one of the most powerful Belgic tribes: Having no strength in cavalry (for even to this day they care naught for that service, but all their power lies in the strength of their infantry), the easier to hamper the cavalry of their neighbours, whenever these made a raid on them, they cut into young saplings and bent them over, and thus by the thick horizontal growth of boughs, and by intertwining with them brambles and thorns, they contrived that these wall-like hedges should serve them as fortifications which not only could not be penetrated, but not even seen through.A more complicated form of defence was the classic ditch and rampart system.
In A.D. 16, Tacitus reported a border fortification built by the Angrivarii, the Angrivarian Wall, which was erected to defend them against the Cherusci.
As a rule, mediaeval landwehrs consist of one or more impenetrable lines of hedging made of pleached hornbeam – (the Gebück) - underplanted with thorny bushes such as blackthorn, hawthorn, dog rose, brambles or holly – (the Gedörn).
In addition there was also usually a combination of one or more of the following elements: From the time after the Frankish colonisation of Central Europe until the late Late Middle Ages, the creation of fixed sovereign territories ruled by lords and princes led to the establishment of territorial landwehrs which enclosed the land which was legally held by states and settlements.
The territories of Gaue, counties (Zenten), regional magistracies (often coterminous with church parishes), Ämter and even entire states were enclosed by landwehrs in the form of defensive hedges.
Numerous toponyms such as Zarge, Gebück, Wehrholz or Gehag recall different variants of these defensive structures as e.g. hedges, excavation works or staggered constructions.
The main objective of these barriers was to protect the population and their land from the hostile claims, raids, predations and warlike assaults of other princes.
Although the enemy did in fact break into the municipal territory, they did not risk a major attack simply because of the danger, in a counter-attack, of not being able to beat a retreat quickly enough through the narrow breach in the landwehr.
As a border fortification around areas that had been given specific rights, landwehrs had gaps in some places for roads, for counter-attack routes or for trade.
Another design was the so-called Wehrhecke (Wallhecke or Knick), a hedge-planted bank, for the maintenance of which a tax called Knickgeld was raised.
In Hesse, at the end of the 17th century, many villages on important roads or by borders, had fortifications, excluding any fortified churches, as a Hessian chronicler described in 1697: Today is almost the majority of large districts and villages in Hesse are surrounded by a moat and embankment / so that they can defend themselves against minor attacks.The fortification could be made of fences (known as Etter or Dorfetter), hedges, bank and ditch (dry as well as wet) and gates.
This was also used as the first obstacle on the approach of castles, town and city walls, and schanzen, and was made of felled trees and cut logs, shrubs and thorns.
Important roads passing through the landwehr at entry points were guarded with so-called barriers (Schlägen) and other reinforcements such as watchtowers.
In the case of the over 100-kilometre-long Westphalian Landwehr in the Teutoburg Forest, punishments ranged from cutting off the right hand to the death penalty.
These border installations were constantly renewed and maintained until the 18th century and, in times of extreme danger, even reinforced and turned into fortifications.
In 1813 in Prussia, the obligation to defend the earthworks, which were slighted under Napoleon but nevertheless remained functional, became part of the general service duties of the military formations of the Prussian Landwehr (a territorial force not to be confused with the subject of this article).
In many cases the field fortifications of the Landwehr troops were abandoned after the end of an armed conflict or after the abolition of an official district, and the hedges and woods burned to make charcoal.