help
from the near by splinterproofs, dugouts, etc., before the enemy can
make his way through the obstacles. It has been found from experience
in the European war that as long as shells are directed at the
trenches no danger of attack is feared but, when the shells are
concentrated against the obstacles the trenches are manned and
preparations are made to resist an assault.

=1175. Location.= Obstacles must be so located that they will be
exposed to the defenders' fire, and should be sheltered as far as
possible from the enemy's artillery fire. They should be difficult to
remove or destroy, should afford no cover for the enemy, and should
not obstruct counter attacks. No obstacle should be more than 100
yards from the defender's trench. Care must be taken not to place them
so close to the trench that hand grenades can be thrown into the
trench from beyond the obstacle. Obstacles may be placed in one, two
or three lines. As far as possible they should be concealed so that
they will not betray the location of the trench.

=1176. Kinds of Obstacles.= The following are the most common kinds of
obstacles:--

=Abatis= consisting of trees lying parallel to each other with the
branches pointing in the general direction of approach and interlaced.
All leaves and small twigs should be removed and the stiff ends of
branches pointed.

Abatis on open ground is most conveniently made of branches about 15
feet long. The branches are staked or tied down and the butts anchored
by covering them with earth. Barbed wire may be interlaced among the
branches. Successive rows are placed, the branches of one extending
over the trunks of the one in front, so as to make the abatis 5 feet
high and as wide as desired. It is better to place the abatis in a
natural depression or a ditch, for concealment and protection from
fire. If exposed to artillery, an abatis must be protected either as
above or else by raising a glacis in front of it. Fig. 1 shows a
typical form of abatis with a glacis in front. An abatis formed by
felling trees toward the enemy, leaving the butt hanging to the stump,
the branches prepared as before, is called =a slashing=, Fig. 2. It
gives cover, and should be well flanked.

[Illustration: Fig. 1]

[Illustration: Fig. 2]

=1177. A palisade= is a man-tight fence of posts. Round poles 4 to 6
inches in diameter at the large end are best. If the sticks run 5 to 8
inches, they may be split. If defended from the rear, pal