Sometimes, such as during the Wars of Scottish Independence and the English Civil War slighting are carried out on a systematic basis as part of a policy by one or both sides to deny the use of fortified places to their enemies.
In England during the Middle Ages adulterine (unauthorised) castles if captured by the king would usually be slighted. During the Wars of Scottish Independence King Robert the Bruce adopted a strategy of slighting Scottish castles to prevent them being occupied by the English. A strategy of slighting castles in the Levant was also adopted by the Mamelukes in their wars with the Crusaders.
Treaty of Edinburgh 1560
Under the terms of The concessions of Francis and Mary to the nobility and the people of Scotland and the Treaty of Edinburgh in July 1560, various fortified places were designated for demolition to prevent their use by French and English forces. These included the recent fortifications at Dunbar Castle, Leith and Eyemouth. On the island of Inchkeith a token garrison of 60 French soldiers were allowed to remain for a time. Inchkeith and Dunbar were finally slighted in 1567.
English Civil War
During the English Civil War many castles and fortified houses were slighted by the Parliamentarians to stop them being used by the Royalists. Most of the destruction was in Wales, the Midlands, and Yorkshire e.g. Pontefract Castle. The coastal fortifications were spared by the Commonwealth, as they might have been useful for hindering a Royalist or foreign invasion.
Situated on the left bank of the Rhine, Burg Rheinfels was started in 1245 by Count Diether V of Katzenelnbogen. By the late 17th century it was a fortress complex. It was the only Rhineland fortress to hold out against the French in the War of the Palatine Succession (1688–1697). During the French Revolutionary Wars, the left bank of the Rhine was annexed by the French Republic and incorporated into France as the department of Rhin-et-Moselle. Under the orders of the French Revolutionary government, Burg Rheinfels was slighted in 1797.
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In the 19th-century many of the obsolete fortifications were slighted in order to provide more space in the area for growing cities. This process of eliminating urban fortifications is specifically referred to as defortification. The resulting slag bricks, clinker, boulders, etc. served as building material for construction. The slighting was carried out by the mechanical removal of walls and ramparts, the leveling of trenches and, if necessary, by blasting. Most of the time, the land on which the fortifications stood was used as parks and green spaces (promenades) or (ring) roads.
- Hull 2008, p. 86.
- Manganiello 2004, p. 498.
- Lowry 2006, p. 29.
- Perry & Blackburn 2000, p. 321.
- Muir 1997, p. 173.
- Traquar, Peter Freedom's Sword p. 159
- Haynes, Samuel, ed., A Collection of State Papers left by William Cecil, 1542-1570, London (1740), see p. 354; letter summarising the finalised treaty of Edinburgh.
- Flintham 2011, Fortified Places: Edinburgh cites Cullen 1988, p. 1
- Guthrie 1768, pp. 124, ff.
- Calendar State Papers Scotland, vol.1 (1898), p.862, 452, 454
- Pollard & Banks 2009, p. 112.
- Castle 1999, p. 101.
- Castle, Alan (1999). Walking the River Rhine trail, Germany. Mountain Walking Series (illustrated ed.). Cicerone Press Limited. pp. 100, 101. ISBN 978-1-85284-276-5.
- Perry, David R.; Blackburn, Mark A. S. (2000). Castle Park, Dunbar: two thousand years on a fortified headland, Part 4. Monograph series - Society of Antiquaries of Scot land 16 (illustrated ed.). Society Antiquaries Scotland. p. 321. ISBN 978-0-903903-16-5.
- Lowry, Bernard (2006). Discovering Fortifications: from the Tudors to the Cold War. Discovering Series; 296. Princes Risborough: Shire. p. 29. ISBN 0-7478-0651-9.
- Flintham, David (5 July 2011). Goode, Dominic, ed. Fortified "Fortified Places: Edinburgh". Fortified Places.
- Guthrie, William (1768). A general history of Scotland from the earliest accounts to the present time 6. A. Hamilton. pp. 124, ff.
- Hull, Lise (2008). Understanding the Castle Ruins of England and Wales: How to Interpret the History and Meaning of Masonry and Earthworks. McFarland. p. 86. ISBN 9780786452767.
- Manganiello, Stephen C. (2004). The Concise Encyclopedia of the Revolutions and Wars of England, Scotland, and Ireland, 1639-1660. Lanham, Md: Scarecrow Press. p. 498. ISBN 0-8108-5100-8.
- Muir, Richard (1997). The Yorkshire Countryside: a landscape history. Edinburgh: Edinburgh University Press. p. 173. ISBN 1-85331-198-7.
- Pollard, Tony; Banks, Iain (2009). "Bastions and barbed wire". Journal of Conflict Archaeology (BRILL): 112. ISBN 90-04-17360-9.