In six weeks the Turkish troops, under the direction of Tewfik Bey, had constructed the most elaborate and perfect system of field fortification that the world had ever seen--a system which utterly routed the old military idea that a bold and well reinforced attack must always succeed against a defended position. It may be as well to briefly describe the main features in the construction of these works as they appeared to an untechnical observer. The usual type of redoubt was a large quadrangular fort, the walls of which were about seven feet high on the outside, and about twenty feet in thickness, the earth of which the walls were formed being a stiff loam, admirably suited for the work. Field-pieces were mounted inside the fort and fired through embrasures protected by bonnettes. The troops fired over the top of the parapet from a banquette reached by steps from the floor which was excavated below the level of the ground outside. The Grivitza redoubt, which was one of the largest, was a perfect square, each side of which was about fifty yards in length. Inside, the redoubt was divided into four compartments by a huge traverse of earth about eight feet thick, which was designed to protect the defenders from reverse fire. Communication between the four compartments was afforded by narrow passages left open between the cross-walls and the exterior wall. The ammunition magazine was stored in a great subterranean chamber excavated underneath the massive cross-walls; and so efficacious was this mode of storing the cartridges, that during the four days' bombardment only two explosions occurred, although it is computed that the Russians fired at least three hundred thousand shells into the redoubts. In the Ibrahim Bey redoubt a segment of a shell found its way into the magazine, which blew up during the height of the attack, killing forty of the defenders, Colonel Ibrahim Bey himself falling at the head of his men soon afterwards. In the Yunuz Bey redoubt in the extreme south-west there was also a disastrous explosion. Yunuz Bey, who commanded all the Krishin redoubts, survived the assault of Skobeleff and was decorated for personal bravery, together with Tewfik Bey, after the battle.