Barricades. These are used for the defense of streets, roads, bridges, etc., and are made of any available materials, including furniture and vehicles, either overthrown or with wheels removed, carts filled with earth, railings, bales of goods, etc. Where trees are growing along the roadside, fell them across it and entangle with wire.
It must be kept in mind, though, that passages are required through these barricades to allow outposts to advance or retreat, that these passages, viewed from the front, must not appear as openings. To avoid this the barricade should be made in two parts, one overlapping the other. Sometimes, where there is a gap in a row of houses, or a sharp bend in the road, a barricade may be made in one part and a passage round one end left for traffic.
Inundations. They may be formed by damming streams at convenient points, specially in the valleys, or by damming up the arches of bridges. In the latter case, care must be taken not to endanger the stability of the bridge. The ditches of field works form a good obstacle when flooded. Destroyed trenches in front of a breastworks may be filled with water, and with barbed wire thrown into it, will prove an effective obstacle.
Fougasses. These are used in connection with obstacles and are really land mines loaded with stones, bricks, etc. An excavation is made in conical shape with an axis inclined to about 40 degrees toward the enemy horizon. A box of powder is then placed in a recess at the bottom and on the box is placed a wooden platform or shield 3 to 4 inches thick, over which stones are piled.
A fuse is placed in a groove cut at the back of the excavation. A line of least resistance must be so arranged that by placing the excavated earth on the back edge of the fougasse, the powder will act in the direction of the axis and not vertically. A fougasse charged with 80 pounds of powder may be constructed in this manner to throw five tons of brick and stone over a surface about 160 yards long by 120 yards wide.
All of the foregoing are labors of working parties, as well as construction of dugouts, carrying of supplies, ammunition, etc., drainage and building of the trenches and the many other jobs behind the lines. Always, no matter how small the job, careful forethought must be given to the planning and arrangement necessary to carry it out.
ORGANIZATION OF BOMBING SQUADS
Every infantry soldier must and does receive instruction in grenade throwing. Some men do not possess the temperament and qualifications necessary to make efficient bombers, and for this reason in every platoon there should be a bombing squad of one N. C. O. and 8 men, with a higher degree of training and efficiency as bomb throwers than the remainder, although all hope must not be given up for the remainder.
These men are available either to work with the platoon or to provide a reserve of bombers for any special job, such as raids, cutting-out parties, and clearing trenches just occupied. Only the very best men in each platoon should be chosen, taking into consideration physique, courage and steadiness, although it is not always the big man physically that makes the best bomber. The responsibility for the training of these men rests with the battalion and company commanders.