Menno, baron van Coehoorn (1641 - March 17, 1704), Dutch soldier and military engineer, of Swedish extraction. He made a number of weaponry inovations in siege warfare and fortification techniques.

He was born at Leeuwarden in Friesland. He received an excellent military and general education, and at the age of sixteen became a captain in the Dutch army. In Anglo-Dutch Wars he took part in the defence of Maastricht in 1673 and in the siege of Grave in 1674, where the small mortars (called coehorns) invented by him caused the French garrison considerable trouble. He was made a colonel for his gallant conduct at the battle of Seneffe (1674), and was present also at the battles of Cassel (1677) and Saint Denis (1678).

The circumstances of the time and the country turned Coehoorns attention to the art of fortification, and the events of the late war showed him that existing methods could no longer be relied upon. His first published work, Versterchinge de Vijfhoeks met alle syne Buytenwerken (Leeuwarden, 1682), at once aroused attention, and involved the author in a lively controversy with a rival engineer, Louys Paan (Leeuwarden, 1682, 1683; copies are in the library of the Dutch ministry of war). The military authorities were much interested in this, and entrusted Coehoorn with the reconstruction of several fortresses in the Netherlands. This task he continued throughout his career; and his experience in the work made him the worthy rival of his great contemporary Vauban. He formulated his ideas a little later in his chief work, New fortress Construction (Nieuwe Vestingbouw, Leeuwarden, 1685), in which he laid down three systems, the characteristic feature of which was the multiplicity and great saliency of the works, which were calculated and in principle are still eminently suited for, flat and almost marshy sites such as those in the Low Countries.

He borrowed many of the details from the works of his Dutch predecessor Freytag, of Albrecht Drer, and of the German engineer Speckle, and in general he aimed rather at the adaptation of his principles to the requirements of individual sites than at producing a geometrically and theoretically perfect fortress. Throughout his career he never hesitated to depart from his own rules in dealing with exceptional cases, such as that of Groningen. Subsequent editions of Nieuwe Vestingbouw appeared in Dutch (1702, and frequently afterwards), English (London, 1705), French (Wesel, 1705), and German (Dusseldorf, 1709).

In War of the Grand Alliance (1689 - 1697) Coehoorn served as a brigadier. At the battle of Fleurus he greatly distinguished himself, and in 1692 he defended Namur, a fortress of his own creation. Namur was taken by Vauban; but the Dutch engineer had his revenge three years later, when the place, on which in the meantime Vauban had lavished his skill, fell to his attack. Coehoorn became lieutenant-general and inspector-general of the Netherlands fortresses, and the high-German peoples as well as his own countrymen honored him. He commanded a corps in the army of the duke of Marlborough from 1701 to 1703, and in the constant siege warfare of these campaigns in the Low Countries his technical skill was of the highest value. The swift reduction of the fortress of Bonn and the siege of Huy in 1703 were his crowning successes. At the opening of his following campaign he was on his way to confer with Marlborough when he died of apoplexy at Wijkel.

His first system was applied to numerous places in Holland, notably Nijmegen, Breda and Bergen op Zoom. Mannheim in Germany was also fortified in this way, while the second system was applied to Belgrade and Temesvar in eastern Europe.

His son, Gosewijn Theodor van Coehoorn , wrote a biography (re-edited Syperstein, Leeuwarden, 1860).

External links

• 1911 Encyclopædia Britannica:COEHOORN, MENNO, BARON VAN