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, _Nieuwe Vestingbouw op en natte of lage horizont_, &c.
(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 of the Low
Countries. He borrowed many of the details from the works of his Dutch
predecessor Freytag, of Albrecht Durer, 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; and 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).

From 1688 to the treaty of Ryswick 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 honoured 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 on the 17th of March 1704.

His "first system" was applied to numerous places in Holland, notably
Nijmwegen, Breda and Bergen-op-Zoom. Mannheim in Germany