to make part of the covered way where the breaching ,s are to be placed, they mu8 firs be taken. The accompanying plan will aid in explaining practical siege operations, ihe at- SSrS made on bastion A, and as the adm- r'cnt demilunes D, D, those on the right and left of A, place the covered way of this point SIEGE vent ingress and egress, the other those re- quired to gain possession of the place; but for convenience they are ordinarily classed into three parts, called the first, second, and third periods. The first period comprises the in- vestment and the encampment of the besieging army around the place; the second all the works from the opening of the trenches until the completion of the third parallel ; and the third all subsequent measures until the place is taken. The investment is performed by de- taching a strong corps, who, moving quickly and secretly, suddenly surround the place, seize all avenues of approach, cut off all com- munications, and secure everything that may be of service to the defence. The main army follows and in- trenches in positions around the place out- side of cannon range. The intrenchments ordinarily form two lines, between which the besieging army places its camps, and are called lines of circumvallation and countervalla- tion. They may be continuous or with intervals, the out- er line being used to prevent succors, and the inner to re- sist the attacks of the garrison. This method of construct- ing lines and enclo- sing the army be- tween them was used by the an- cients, and fell into disuse during the middle ages. It was revived in the 16th century by the princes of Nassau, and has been prac- tised more or less in a reentrant angle, these demilunes must be I ever since. These lines not only enable the of attack. B. Adjacent bastion. D. Demilune of front of attack. C. Col in'-. K. F. Troncn connecting first and second parallels. K, K. Demi-pa M, M, M. Enfilading, counter, and mortar batteries. T. T. Troops, called guards 1. Half of Plan of regular Approaches against a Front of Attack. Demilune of front of attack. C. Collateral larnllels. of the trenches, protecting the workmen on opening the first parallel. 9. Section showing Slopes and Dimensions of Profile of Approach by simple Trench. A bastion corresponding to B, demilunes to C and D, and approaches on the left of A, are supposed to be indicated and to form the whole front of attack. taken before the bastion can be breached. This bast i( Hi and the adjacent demilunes with their outworks must be taken by breach or anl tin* fire from the collateral de- <' and bastion B shown in the plan, and the corresponding ones on the left not shown, must be kept under by opposing bat- teries during those operations, to enable the besiegers to carry on their work successfully. iches are made on the three salients, A. h. !>, m<l thete by parallels
- o bodies of troops to protect the
workni-n an<l r.-p.-l sorties. The siege opera- tions may be divided into two general parts, one including all the measures taken to pre- besieging army to repulse detachments that try to reenforce the place, but are also useful where the besieging army is forced to take up weak positions to complete the investment. The strength of the besieged work, the nature of the ground, and the facilities for transport- ing troops and supplies from the depots are governing considerations in selecting the front of attack. Salients are usually the weakest- points of a fortification ; low, marshy soil and rocky ground present the greatest difficulties in constructing siege works. The second pe- riod begins with the opening of the trenches, which is done by digging a ditch or trench, between 600 and 700 yards from the most
