from it, all concealed as far as possible from enemy
aviators. There were also many dummy batteries, so that if the enemy
air scout saw a gun or group of guns, he had no way of telling whether
they were real or imitation.

In such an instance before the actual advance of the troops the fire of
all these guns is concentrated along parallel lines to the enemy
trenches, first, second and sometimes third. Each gun has its work
mapped out for it in advance on a map covered with tiny squares. The
actual point may be well beyond view of the gunners. The shell is landed
in its appointed square solely on mathematical calculation. The
commander of each gun knows, for instance, that he must fire into this,
that or the other square for so many minutes or hours, and exactly at a
given minute change his fire to another source.

RAIN OF SHELLS LIKE STREAMS OF WATER.

In effect on the enemy a continuous rain of shells, comparable to
streams of water from hundreds of hoses is poured in a line right down
the trench. At the same time a parallel line of fire is concentrated at
a given distance back of the enemy's first trench and in front of the
second, or in it. This means that the troops in the first line must not
only take their bombardment without hope of retreat or escape, but that
it is impossible to get reinforcements to them through the second
curtain.

When it is calculated that the first line has been destroyed or
demoralized, the troops leap from their trenches and advance strictly
according to schedule over the ground between the opposing trenches.
Their arrival at the enemy's first trench is timed to the second, and
just as they are on the verge of plunging into their own curtain of fire
this latter is gradually thrown forward, forming a screen between the
newly captured trench and the enemy's second line. This means two
curtains of fire through which the enemy would have to advance to
counter-attack.

Time is given to rout out what remains of the enemy from the first line
dugouts, and then the troops advance again. In the meantime the curtain
of fire has preceded them as before, moving up to the line of drum fire
which has been playing on the second line of trenches or just in front
of it. If any of the enemy have attempted to flee before the attack from
the first line they are caught between these two barrages which are
gradually brought together.

When the first and second lines of fire have been brought together t