Quadrilateral

In military language, an expre ion designating a combination of four fortre es, not nece arily connected together, but mutually supporting each other; and from the fact that if one be attacked, the garrisons of the others, unle carefully observed, will hara the besiegers, rendering it nece ary that a very large army should be employed to turn the combined position. As a remarkable instance, and a very powerful one, may be cited the celebrated quadrilateral in Venetia, comprising the four strong posts of Mantua, Verona, Peschiera, and Legnago. These form a sort of outwork to the bastion which the southern mountains of the Tyrol constitute, and divide the north plain of the Po into two sections by a most powerful barrier. Napoleon III., in 1859, even after the victories of Magenta and Solferino, hesitated to attack this quadrilateral.