Modern wars have been marked by sharp aggressive campaigns and great battles in the open field, with few close and long-continued sieges.

The subject of siege-works has therefore attracted less popular attention than was formerly devoted to it.

Fort Wagner, Vicksburg, Petersburg, Strasburg, Belfort, Paris, Plevna, and GÉok TÉpÉ have shown, however, that at their respective dates regular siege and mining operations were necessary to reduce either permanent or field fortifications, if well equipped and defended.

The volume of fire delivered by the small arms and machine guns now in use has made an open assault upon a well-supplied and well-defended parapet, under ordinary circumstances, a hopeless undertaking, and has necessitated more deliberate methods of attack.

The increased accuracy and penetration of modern cannon have rendered obsolete many of the older methods of making regular approaches.

The newer constructions described herein, while giving greater protection to the attack, are in general slower in their advance than those previously used. This seems, however, to be an unavoidable evil, which is mitigated only by taking advantage of every opportunity for rapid advance offered by the errors of the defence.

It is not to be inferred that light field works and lines will in the general case require for their attack a system of regular approaches; but trenches and saps may be necessary for placing a battery or parapet in a commanding position or one favorable for enfilade, or for giving a covered approach over an exposed ridge; and their frequent employment may be expected on future fields.

The destructive effect of grenades and Coehorn shells charged with high explosives will doubtless in many cases check or stop the advance of saps and trenches, and necessitate the use of blinded approaches or mining-galleries in stubbornly contested sieges. The successful application of mines at GÉok TÉpÉ will doubtless lead to their future employment under similar circumstances. In the close attack upon a shielded casemate or disappearing turret their use seems a necessity, and when these defences are founded on rock or massive concrete foundations, tunnelling operations by drilling and blasting will be required. When practicable they will be expedited by the use of power-drills driven by electricity.

It seems hardly necessary to add, that in sapping and mining operations, as in all other branches of military engineering, all new and improved inventions and methods which are applicable to the work on hand will be used, as a matter of course.

The thickness of cover given in the text is based upon the penetrations of the hostile projectiles.

For ready reference the maximum penetrations obtained in experimental firing up to this date (1894) are given herewith, viz.:

Service bullets, copper or German-silver jacket, of 6.5 to 8 mm. calibre, initial velocity from 2000 to 2550 f. s.:

French authorities give a muzzle penetration of 12 mm. = 0´´.473 in iron plates for the Lebel bullet. No published experiments confirm this.

But few experiments seem to have been made to determine the penetration of the projectile of field and siege guns into earth, and the published data are very meagre and unsatisfactory.

The German Engineer’s Handbook (Pionier Taschenbuch, 1892) prescribes the following thicknesses of parapets for cover against small-arm and cannon fire, viz.:

English authorities report craters of 21 feet length and 8 feet depth blown out from an earth parapet by a single 200-lb. 8-in. howitzer shell. They also state that the projectile of the pneumatic dynamite gun has penetrated 40 feet of earth.

Owing to the rapid development of ordnance the current scientific and military periodicals are in general the only source from which the latest results in penetration, etc., can be obtained.