2d. The operations of the two parties from the opening of the trenches
to the establishment of the third parallel.

3d. From the completion of the third parallel to the reduction of the
place.

_First period._ The object of the _investment of the place_ is to cut
off all communication between the work and the exterior, thus preventing
it from receiving succors, provisions, and military munitions, and also
to facilitate a close reconnoissance of the place by the engineers, who
should always accompany the investing corps, and pursue their labors
under its protection. This corps should be composed chiefly of light
troops--cavalry, light infantry, horse artillery, "brigades of engineers
and mounted sappers,"--who march in advance of the besieging army, and,
by a sudden movement, surround the work, seize upon all the avenues of
approach, and carry off every thing without the work that can be of
service either to the garrison or to the besiegers. To effect this
object, the enterprise must be conducted with secrecy and dispatch.

The investing corps is now distributed around the work in the most
favorable positions for cutting off all access to it, and also to
prevent any communication with the exterior by detachments from the
garrison, and even single individuals are sent out to give intelligence
to a succoring army or to reconnoitre the operations of the besieging
corps. These posts and sentinels, called the _daily cordon_, are placed
some mile or mile and a half from the work, and beyond the reach of the
guns. But in the night-time these posts are insufficient to accomplish
their object, and consequently as soon as it is dark the troops move up
as close to the work as possible without being exposed to the fire of
musketry. This arrangement constitutes the _nightly cordon_.

By the time the main army arrives the reconnoissance will be
sufficiently complete to enable the chief engineer to lay before the
general the outline of his plan of attack, so as to establish the
position of his depots and camp. These will be placed some two miles
from the work, according to the nature of the ground. As they occupy a
considerable extent of ground around the work, it will generally be
necessary to form intrenchments strong enough to prevent succors of
troops, provisions, &c., from being thrown into the place, and also to
restrain the excursions of the garrison. The works thrown up between the
camp and besieged place are termed the