COEHOORN, or COHORN, MENNO, Baron Van, called. the Dutch Vauban, was b. at Lettingastate, near Leeuwarden, in 1641, and studied fortification and mathematics under his uncle Bernardus Fullenins, then professor of these sciences at Franeker. Prince Henry Casimir, stadtholder of Friesland, apprised of the youth's great abilities, appointed him. iu his 16th year, cant. of a company of infantry; and in 1674, C. greatly distinguished himself at the siege of Maestricht, and in various battles. At the siege of Grave, in 1674. he demonstrated that small portable mortars might be advantageously employed (see next art.); and also that the combined effect of a certain mass of projec tiles is much greater than the effect produced by a successive discharge of the separate projectiles composing the mass. The application of this principle distingt ishes the opera tions of Coehoorn. C. covered himself with honor before Kaiserwerth (June) and Bonn Oct., 1689), and the elector of Brandenburg wanted to make him maj.gen., a promotion he refused. He also distinguished himself in the battle of Flenrus, (July 1, 1690). He was
now for sonic time in disgrace, but was soon sought again by William III. lie fortified Namur, and defended his own intrenchment "William" against Vauban in 1692; besieged that fortress in 1693, and retook it; was appointed bent:gen. and director-in chief of the Dutch fortifications, and fortified several towns, of which Bergen-op-Zoom may be considered his masterpiece. Iu 1102, he annihilated the French lines near St. Donat. He died at the Hague, Mar. 17, 1104. His principal works are The New Sys tem of Fortification (Leeuwarden, 1685) and Tide Pentagon.
COE'HORNS—named from the military engineer who invented or Introduced them— are small howitzers or mortars, generally 4 in. caliber. These implements of a r, being easily moved and adjusted, and taking 'fide powder, are found very useful in sieges, if grouped in great number. A battery of 30 or 40 0., by pouring their small shells or grenades into the outworks of a fortress, may prevent the garrison from effecting a strong occupation, or making a demonstration.