First French editions of two complementary works in matching format and layout by Simon Stevin, on the layout of army camps and on hydraulic engineering for fortifications (in particular the use of pivoted sluices for deepening waterways, draining land and operating locks). The Castrametation provides a window into daily life in the Dutch army during the Eighty Years' War of independence from Spain, shedding light on both the physical arrangement of troops, supplies, armaments, etc., and the rules that soldiers were expected to follow. The Fortification par escluses both reflects and helped to establish the Dutch mastery of the seas and waterways, which was unique among nations at this date. While the numerous fortification plans are presented as general types to illustrate principles, many are based on actual Dutch cities. The book therefore provides Stevin's analysis of the strtegic situation of many Dutch cities and the ways their security could be improved by hydraulic engineering. Both works were published during the Twelve Years' Truce (1609-1621), partly in anticipation of the renewal of hostilities in 1621 and therefore the need to improve the Dutch defences.
With ink owner's additions to the fortification plan on F3 of the second work. Four of the fortification plans also have some additions drawn over them (perhaps somewhat later) in pencil. With bookplate. The Castrametation lacks 2 preliminary leaves, with the portrait and coat-of-arms of Maurits of Nassau, Prince of Orange. With a water stain at the head of the leaves in the first half, and slightly browned throughout. The binding shows a few stains and scuffmarks, with one tape broken at one joint and the paper label tattered, but is otherwise good. First French editions of two important Dutch military works. Bierens de Haan 4576 & 4577; Simoni S258; Sloos, Warfare 8014 & 8015; STCN (5 & 4 copies); cf. Jähns I, 127 .